diff --git a/src/accessiweather/config/config_manager.py b/src/accessiweather/config/config_manager.py
index 4fa5920b..17dfe537 100644
--- a/src/accessiweather/config/config_manager.py
+++ b/src/accessiweather/config/config_manager.py
@@ -278,10 +278,21 @@ def update_settings(self, **kwargs) -> bool:
         return self._settings.update_settings(**kwargs)
 
     def add_location(
-        self, name: str, latitude: float, longitude: float, country_code: str | None = None
+        self,
+        name: str,
+        latitude: float,
+        longitude: float,
+        country_code: str | None = None,
+        marine_mode: bool = False,
     ) -> bool:
         """Add a new location."""
-        return self._locations.add_location(name, latitude, longitude, country_code)
+        return self._locations.add_location(
+            name,
+            latitude,
+            longitude,
+            country_code,
+            marine_mode=marine_mode,
+        )
 
     def remove_location(self, name: str) -> bool:
         """Remove a location."""
diff --git a/src/accessiweather/config/locations.py b/src/accessiweather/config/locations.py
index 764c3e28..9a5dd61a 100644
--- a/src/accessiweather/config/locations.py
+++ b/src/accessiweather/config/locations.py
@@ -30,6 +30,7 @@ def add_location(
         latitude: float,
         longitude: float,
         country_code: str | None = None,
+        marine_mode: bool = False,
     ) -> bool:
         """Add a new location if it doesn't already exist."""
         config = self._manager.get_config()
@@ -44,6 +45,7 @@ def add_location(
             latitude=latitude,
             longitude=longitude,
             country_code=country_code,
+            marine_mode=marine_mode,
         )
         config.locations.append(new_location)
 
diff --git a/src/accessiweather/display/presentation/forecast.py b/src/accessiweather/display/presentation/forecast.py
index 8d70b548..6607dd17 100644
--- a/src/accessiweather/display/presentation/forecast.py
+++ b/src/accessiweather/display/presentation/forecast.py
@@ -6,7 +6,14 @@
 from datetime import datetime, tzinfo
 
 from ...forecast_confidence import ForecastConfidence
-from ...models import AppSettings, Forecast, ForecastPeriod, HourlyForecast, Location
+from ...models import (
+    AppSettings,
+    Forecast,
+    ForecastPeriod,
+    HourlyForecast,
+    Location,
+    MarineForecast,
+)
 from ...utils import TemperatureUnit, calculate_dewpoint
 from ...utils.unit_utils import format_precipitation, format_wind_speed
 from ..weather_presenter import (
@@ -105,6 +112,7 @@ def build_forecast(
     unit_pref: TemperatureUnit,
     settings: AppSettings | None = None,
     *,
+    marine: MarineForecast | None = None,
     confidence: ForecastConfidence | None = None,
 ) -> ForecastPresentation:
     """Create a structured forecast including optional hourly highlights."""
@@ -277,7 +285,32 @@ def build_forecast(
         hours=hourly_hours,
         summary_line=hourly_summary_line,
     )
+
+    marine_summary = None
+    marine_highlights: list[str] = []
+    marine_section_text = ""
+    if marine and marine.has_data():
+        marine_lines = [f"Marine conditions for {location.name}:"]
+        if marine.zone_name:
+            zone_label = marine.zone_name
+            if marine.zone_id:
+                zone_label = f"{zone_label} ({marine.zone_id})"
+            marine_lines.append(f"Marine zone: {zone_label}")
+        marine_summary = marine.forecast_summary
+        if marine_summary:
+            marine_lines.append(f"Summary: {marine_summary}")
+        marine_highlights = marine.highlights[:4]
+        if marine_highlights:
+            marine_lines.append("Wind and wave highlights:")
+            marine_lines.extend(f"  • {highlight}" for highlight in marine_highlights)
+        for period in marine.periods[:3]:
+            if period.summary:
+                marine_lines.append(f"{period.name}: {wrap_text(period.summary, 80)}")
+        marine_section_text = "\n".join(marine_lines).rstrip()
+
     fallback_sections = [daily_section_text]
+    if marine_section_text:
+        fallback_sections.append(marine_section_text)
     if hourly_section_text:
         fallback_sections.append(hourly_section_text)
     fallback_text = "\n\n".join(section for section in fallback_sections if section).rstrip()
@@ -291,6 +324,9 @@ def build_forecast(
         fallback_text=fallback_text,
         daily_section_text=daily_section_text,
         hourly_section_text=hourly_section_text,
+        marine_section_text=marine_section_text,
+        marine_summary=marine_summary,
+        marine_highlights=marine_highlights,
         confidence_label=confidence_label,
         summary=summary_line,
     )
diff --git a/src/accessiweather/display/presentation/html_formatters.py b/src/accessiweather/display/presentation/html_formatters.py
index 92194abf..60eab97e 100644
--- a/src/accessiweather/display/presentation/html_formatters.py
+++ b/src/accessiweather/display/presentation/html_formatters.py
@@ -133,6 +133,23 @@
     color: #888;
     font-style: italic;
 }
+.marine-section {
+    margin-bottom: 16px;
+    padding: 8px;
+    background-color: #f3f8ff;
+    border-radius: 4px;
+    border: 1px solid #d7e7ff;
+}
+.marine-section ul {
+    margin: 6px 0 0 18px;
+    padding: 0;
+}
+.marine-section li {
+    margin-bottom: 4px;
+}
+.marine-period {
+    margin-top: 8px;
+}
 """
 
 
@@ -259,6 +276,54 @@ def generate_forecast_html(presentation: ForecastPresentation | None) -> str:
 <div class="hourly-grid" role="list">
 {"".join(hourly_items)}
 </div>
+</section>"""
+
+    # Build marine section if available
+    marine_html = ""
+    if presentation.marine_section_text:
+        marine_summary_html = ""
+        if presentation.marine_summary:
+            marine_summary_html = (
+                f'<p class="description">{_escape_html(presentation.marine_summary)}</p>'
+            )
+
+        marine_highlights_html = ""
+        if presentation.marine_highlights:
+            marine_items = "".join(
+                f"<li>{_escape_html(highlight)}</li>"
+                for highlight in presentation.marine_highlights
+            )
+            marine_highlights_html = f"""
+<h3>Marine Highlights</h3>
+<ul>
+{marine_items}
+</ul>"""
+
+        period_lines = [
+            line.strip()
+            for line in presentation.marine_section_text.splitlines()
+            if line.strip()
+            and ":" in line
+            and not line.startswith(
+                (
+                    "Marine conditions",
+                    "Marine zone:",
+                    "Summary:",
+                    "Wind and wave highlights:",
+                    "•",
+                )
+            )
+        ]
+        marine_periods_html = "".join(
+            f'<p class="marine-period">{_escape_html(line)}</p>' for line in period_lines
+        )
+
+        marine_html = f"""
+<section class="marine-section" aria-label="Marine forecast">
+<h2>Marine Forecast</h2>
+{marine_summary_html}
+{marine_highlights_html}
+{marine_periods_html}
 </section>"""
 
     # Build forecast periods
@@ -295,6 +360,7 @@ def generate_forecast_html(presentation: ForecastPresentation | None) -> str:
 <section role="region" aria-label="{title}">
 <h1>{title}</h1>
 {hourly_html}
+{marine_html}
 {periods_html}
 {generated_html}
 </section>
diff --git a/src/accessiweather/display/weather_presenter.py b/src/accessiweather/display/weather_presenter.py
index 15a2bf4d..0448054c 100644
--- a/src/accessiweather/display/weather_presenter.py
+++ b/src/accessiweather/display/weather_presenter.py
@@ -25,6 +25,7 @@
     Forecast,
     HourlyForecast,
     Location,
+    MarineForecast,
     TrendInsight,
     WeatherAlerts,
     WeatherData,
@@ -105,6 +106,9 @@ class ForecastPresentation:
     fallback_text: str = ""
     daily_section_text: str = ""
     hourly_section_text: str = ""
+    marine_section_text: str = ""
+    marine_summary: str | None = None
+    marine_highlights: list[str] = field(default_factory=list)
     confidence_label: str | None = None
     summary: str | None = None
 
@@ -233,6 +237,7 @@ def present(self, weather_data: WeatherData) -> WeatherPresentation:
                 weather_data.hourly_forecast,
                 weather_data.location,
                 unit_pref,
+                marine=weather_data.marine,
                 confidence=weather_data.forecast_confidence,
             )
             if weather_data.forecast
@@ -308,13 +313,19 @@ def present_forecast(
         forecast: Forecast | None,
         location: Location,
         hourly_forecast: HourlyForecast | None = None,
+        marine: MarineForecast | None = None,
         confidence: ForecastConfidence | None = None,
     ) -> ForecastPresentation | None:
         if not forecast or not forecast.has_data():
             return None
         unit_pref, _unit_system = self._resolve_unit_preferences(location)
         return self._build_forecast(
-            forecast, hourly_forecast, location, unit_pref, confidence=confidence
+            forecast,
+            hourly_forecast,
+            location,
+            unit_pref,
+            marine=marine,
+            confidence=confidence,
         )
 
     def present_alerts(
@@ -365,6 +376,7 @@ def _build_forecast(
         hourly_forecast: HourlyForecast | None,
         location: Location,
         unit_pref: TemperatureUnit,
+        marine: MarineForecast | None = None,
         confidence: ForecastConfidence | None = None,
     ) -> ForecastPresentation:
         return build_forecast(
@@ -373,6 +385,7 @@ def _build_forecast(
             location,
             unit_pref,
             settings=self.settings,
+            marine=marine,
             confidence=confidence,
         )
 
diff --git a/src/accessiweather/models/__init__.py b/src/accessiweather/models/__init__.py
index 12a1b39c..fc575f76 100644
--- a/src/accessiweather/models/__init__.py
+++ b/src/accessiweather/models/__init__.py
@@ -25,6 +25,8 @@
     HourlyForecastPeriod,
     HourlyUVIndex,
     Location,
+    MarineForecast,
+    MarineForecastPeriod,
     MinutelyPrecipitationForecast,
     MinutelyPrecipitationPoint,
     SourceAttribution,
@@ -42,6 +44,8 @@
     "HourlyForecast",
     "HourlyAirQuality",
     "HourlyUVIndex",
+    "MarineForecastPeriod",
+    "MarineForecast",
     "MinutelyPrecipitationPoint",
     "MinutelyPrecipitationForecast",
     "TrendInsight",
diff --git a/src/accessiweather/models/config.py b/src/accessiweather/models/config.py
index 269e2ff0..3aaa8e14 100644
--- a/src/accessiweather/models/config.py
+++ b/src/accessiweather/models/config.py
@@ -636,6 +636,7 @@ def to_dict(self) -> dict:
                     "latitude": loc.latitude,
                     "longitude": loc.longitude,
                     **({"country_code": loc.country_code} if loc.country_code else {}),
+                    **({"marine_mode": True} if loc.marine_mode else {}),
                 }
                 for loc in self.locations
             ],
@@ -648,6 +649,7 @@ def to_dict(self) -> dict:
                     if self.current_location.country_code
                     else {}
                 ),
+                **({"marine_mode": True} if self.current_location.marine_mode else {}),
             }
             if self.current_location
             else None,
@@ -666,6 +668,7 @@ def from_dict(cls, data: dict) -> AppConfig:
                     latitude=loc_data["latitude"],
                     longitude=loc_data["longitude"],
                     country_code=loc_data.get("country_code"),
+                    marine_mode=bool(loc_data.get("marine_mode", False)),
                 )
             )
 
@@ -677,6 +680,7 @@ def from_dict(cls, data: dict) -> AppConfig:
                 latitude=loc_data["latitude"],
                 longitude=loc_data["longitude"],
                 country_code=loc_data.get("country_code"),
+                marine_mode=bool(loc_data.get("marine_mode", False)),
             )
 
         return cls(
diff --git a/src/accessiweather/models/weather.py b/src/accessiweather/models/weather.py
index 222b3ffe..318ae2b0 100644
--- a/src/accessiweather/models/weather.py
+++ b/src/accessiweather/models/weather.py
@@ -130,6 +130,7 @@ class Location:
     longitude: float
     timezone: str | None = None
     country_code: str | None = None
+    marine_mode: bool = False
 
     def __str__(self) -> str:
         return self.name
@@ -532,6 +533,30 @@ def has_taf(self) -> bool:
         )
 
 
+@dataclass
+class MarineForecastPeriod:
+    """Single marine forecast period from an NWS marine zone product."""
+
+    name: str
+    summary: str
+
+
+@dataclass
+class MarineForecast:
+    """Marine zone essentials for a coastal location."""
+
+    zone_id: str | None = None
+    zone_name: str | None = None
+    forecast_summary: str | None = None
+    issued_at: datetime | None = None
+    periods: list[MarineForecastPeriod] = field(default_factory=list)
+    highlights: list[str] = field(default_factory=list)
+
+    def has_data(self) -> bool:
+        """Return True when any marine essentials are available."""
+        return bool(self.forecast_summary or self.zone_name or self.periods or self.highlights)
+
+
 @dataclass
 class WeatherData:
     """Complete weather data for a location."""
@@ -547,6 +572,7 @@ class WeatherData:
     alerts: WeatherAlerts | None = None
     environmental: EnvironmentalConditions | None = None
     aviation: AviationData | None = None
+    marine: MarineForecast | None = None
     trend_insights: list[TrendInsight] = field(default_factory=list)
     stale: bool = False
     stale_since: datetime | None = None
@@ -584,5 +610,6 @@ def has_any_data(self) -> bool:
                 self.alerts and self.alerts.has_alerts(),
                 self.environmental and self.environmental.has_data(),
                 self.aviation and self.aviation.has_taf(),
+                self.marine and self.marine.has_data(),
             ]
         )
diff --git a/src/accessiweather/ui/dialogs/location_dialog.py b/src/accessiweather/ui/dialogs/location_dialog.py
index 8ed0e70a..77fac504 100644
--- a/src/accessiweather/ui/dialogs/location_dialog.py
+++ b/src/accessiweather/ui/dialogs/location_dialog.py
@@ -107,6 +107,15 @@ def _create_ui(self):
         help_text.SetForegroundColour(wx.SystemSettings.GetColour(wx.SYS_COLOUR_GRAYTEXT))
         name_sizer.Add(help_text, 0, wx.TOP, 5)
 
+        self.marine_mode_checkbox = wx.CheckBox(
+            panel,
+            label="Enable Marine Mode for this location (coastal essentials only)",
+        )
+        self.marine_mode_checkbox.SetToolTip(
+            "Adds nearby NWS marine zone summary, wind and wave highlights, and marine advisories."
+        )
+        name_sizer.Add(self.marine_mode_checkbox, 0, wx.TOP, 8)
+
         main_sizer.Add(name_sizer, 0, wx.EXPAND | wx.ALL, 10)
 
         # Search section
@@ -174,6 +183,7 @@ def _setup_accessibility(self):
         self.name_input.SetName("Location name input")
         self.search_input.SetName("Search for location")
         self.results_list.SetName("Search results")
+        self.marine_mode_checkbox.SetName("Enable Marine Mode for this location")
 
     def _on_key(self, event: wx.KeyEvent) -> None:
         """Handle key events."""
@@ -307,7 +317,11 @@ def _on_save(self, event):
 
             # Add location
             success = self.config_manager.add_location(
-                name, latitude, longitude, country_code=country_code
+                name,
+                latitude,
+                longitude,
+                country_code=country_code,
+                marine_mode=self.marine_mode_checkbox.GetValue(),
             )
 
             if success:
diff --git a/src/accessiweather/ui/main_window.py b/src/accessiweather/ui/main_window.py
index 55123e60..91dd725c 100644
--- a/src/accessiweather/ui/main_window.py
+++ b/src/accessiweather/ui/main_window.py
@@ -1201,9 +1201,11 @@ def _on_weather_data_received(self, weather_data) -> None:
 
             # Update forecast
             if presentation.forecast:
-                daily_text = (
-                    presentation.forecast.daily_section_text or "No daily forecast available."
-                )
+                daily_sections = [presentation.forecast.daily_section_text]
+                if presentation.forecast.marine_section_text:
+                    daily_sections.append(presentation.forecast.marine_section_text)
+                daily_text = "\n\n".join(section for section in daily_sections if section).rstrip()
+                daily_text = daily_text or "No daily forecast available."
                 hourly_text = (
                     presentation.forecast.hourly_section_text or "No hourly forecast available."
                 )
diff --git a/src/accessiweather/weather_client_base.py b/src/accessiweather/weather_client_base.py
index da424a05..c23dcab4 100644
--- a/src/accessiweather/weather_client_base.py
+++ b/src/accessiweather/weather_client_base.py
@@ -1174,6 +1174,9 @@ def _launch_enrichment_tasks(
         tasks["aviation"] = asyncio.create_task(
             enrichment.enrich_with_aviation_data(self, weather_data, location)
         )
+        tasks["marine"] = asyncio.create_task(
+            enrichment.enrich_with_marine_data(self, weather_data, location)
+        )
 
         return tasks
 
diff --git a/src/accessiweather/weather_client_enrichment.py b/src/accessiweather/weather_client_enrichment.py
index f997b117..827c7f17 100644
--- a/src/accessiweather/weather_client_enrichment.py
+++ b/src/accessiweather/weather_client_enrichment.py
@@ -3,12 +3,22 @@
 from __future__ import annotations
 
 import logging
+import re
+from datetime import datetime
 from typing import TYPE_CHECKING, Any
 
 from . import weather_client_nws as nws_client
 from .api.avwx_client import AvwxApiError, fetch_avwx_taf, is_us_station
 from .display.presentation.environmental import _get_uv_category
-from .models import AviationData, Location, WeatherAlert, WeatherAlerts, WeatherData
+from .models import (
+    AviationData,
+    Location,
+    MarineForecast,
+    MarineForecastPeriod,
+    WeatherAlert,
+    WeatherAlerts,
+    WeatherData,
+)
 from .utils import decode_taf_text
 
 if TYPE_CHECKING:
@@ -291,6 +301,132 @@ async def get_aviation_weather(
     return aviation
 
 
+_MARINE_HIGHLIGHT_PATTERN = re.compile(
+    r"([^.;]*\b(?:wind|winds|gust|gusts|wave|waves|seas|swell|swells)\b[^.;]*)",
+    re.IGNORECASE,
+)
+
+
+def _build_marine_highlights(periods: list[dict[str, Any]]) -> list[str]:
+    """Extract concise wind and wave highlights from marine text periods."""
+    highlights: list[str] = []
+    seen: set[str] = set()
+    for period in periods:
+        for field in ("shortForecast", "detailedForecast"):
+            text = str(period.get(field) or "").strip()
+            if not text:
+                continue
+            for match in _MARINE_HIGHLIGHT_PATTERN.findall(text):
+                candidate = " ".join(match.split()).strip(" .")
+                if not candidate:
+                    continue
+                normalized = candidate.lower()
+                if normalized in seen:
+                    continue
+                seen.add(normalized)
+                highlights.append(candidate)
+                if len(highlights) >= 4:
+                    return highlights
+    return highlights
+
+
+def _parse_marine_issued_at(value: Any) -> datetime | None:
+    if not value or not isinstance(value, str):
+        return None
+    try:
+        return datetime.fromisoformat(value.replace("Z", "+00:00"))
+    except ValueError:
+        return None
+
+
+async def enrich_with_marine_data(
+    client: WeatherClient, weather_data: WeatherData, location: Location
+) -> None:
+    """Populate marine essentials for coastal locations when marine mode is enabled."""
+    if not getattr(location, "marine_mode", False) or not client._is_us_location(location):
+        return
+
+    try:
+        http_client = client._get_http_client()
+        headers = {"User-Agent": client.user_agent}
+        marine_zone_response = await nws_client._client_get(
+            http_client,
+            f"{client.nws_base_url}/zones",
+            headers=headers,
+            params={"type": "marine", "point": f"{location.latitude},{location.longitude}"},
+        )
+        marine_zone_response.raise_for_status()
+        marine_zone_data = marine_zone_response.json()
+        features = marine_zone_data.get("features") or []
+        if not features:
+            return
+
+        marine_feature = features[0]
+        marine_properties = marine_feature.get("properties", {})
+        zone_id = marine_properties.get("id") or marine_feature.get("id")
+        if not zone_id:
+            return
+
+        marine_forecast_data = await nws_client.get_nws_marine_forecast(
+            "marine",
+            zone_id,
+            client.nws_base_url,
+            client.user_agent,
+            client.timeout,
+            http_client,
+        )
+        if not marine_forecast_data:
+            return
+
+        forecast_properties = marine_forecast_data.get("properties", {})
+        forecast_periods = forecast_properties.get("periods") or []
+        periods = [
+            MarineForecastPeriod(
+                name=str(period.get("name") or "Marine period"),
+                summary=str(
+                    period.get("detailedForecast") or period.get("shortForecast") or ""
+                ).strip(),
+            )
+            for period in forecast_periods[:3]
+            if (period.get("detailedForecast") or period.get("shortForecast"))
+        ]
+        marine = MarineForecast(
+            zone_id=zone_id,
+            zone_name=forecast_properties.get("name") or marine_properties.get("name"),
+            forecast_summary=(
+                str(
+                    forecast_periods[0].get("detailedForecast")
+                    or forecast_periods[0].get("shortForecast")
+                )
+                if forecast_periods
+                else None
+            ),
+            issued_at=_parse_marine_issued_at(forecast_properties.get("updateTime")),
+            periods=periods,
+            highlights=_build_marine_highlights(forecast_periods[:4]),
+        )
+        if marine.has_data():
+            weather_data.marine = marine
+
+        marine_alerts_response = await nws_client._client_get(
+            http_client,
+            f"{client.nws_base_url}/alerts/active",
+            headers=headers,
+            params={"zone": zone_id, "status": "actual"},
+        )
+        marine_alerts_response.raise_for_status()
+        marine_alerts = nws_client.parse_nws_alerts(marine_alerts_response.json())
+        if marine_alerts and marine_alerts.alerts:
+            existing = weather_data.alerts.alerts if weather_data.alerts else []
+            merged: dict[str, WeatherAlert] = {alert.get_unique_id(): alert for alert in existing}
+            for alert in marine_alerts.alerts:
+                alert.source = "NWS Marine"
+                merged.setdefault(alert.get_unique_id(), alert)
+            weather_data.alerts = WeatherAlerts(alerts=list(merged.values()))
+    except Exception as exc:  # noqa: BLE001
+        logger.debug("Failed to fetch marine essentials for %s: %s", location.name, exc)
+
+
 async def enrich_with_aviation_data(
     client: WeatherClient, weather_data: WeatherData, location: Location
 ) -> None:
diff --git a/tests/test_config_manager.py b/tests/test_config_manager.py
index bdd1e666..38e04717 100644
--- a/tests/test_config_manager.py
+++ b/tests/test_config_manager.py
@@ -83,6 +83,29 @@ def test_add_location(self, manager):
         assert len(non_nationwide) == 1
         assert non_nationwide[0].name == "New York"
 
+    def test_add_location_persists_marine_mode_roundtrip(self, manager):
+        """Marine mode should save and reload with locations."""
+        result = manager.add_location(
+            name="Annapolis",
+            latitude=38.9784,
+            longitude=-76.4922,
+            country_code="US",
+            marine_mode=True,
+        )
+        assert result is True
+
+        manager.set_current_location("Annapolis")
+        manager.save_config()
+
+        manager2 = ConfigManager(manager.app, config_dir=manager.config_dir)
+        loaded = manager2.load_config()
+
+        saved_location = next(loc for loc in loaded.locations if loc.name == "Annapolis")
+        assert saved_location.marine_mode is True
+        assert loaded.current_location is not None
+        assert loaded.current_location.name == "Annapolis"
+        assert loaded.current_location.marine_mode is True
+
     def test_add_duplicate_location_fails(self, manager):
         """Test that adding duplicate location fails."""
         manager.add_location("Test", 40.0, -74.0)
diff --git a/tests/test_coverage_fix_pr449.py b/tests/test_coverage_fix_pr449.py
index 913de405..2d135442 100644
--- a/tests/test_coverage_fix_pr449.py
+++ b/tests/test_coverage_fix_pr449.py
@@ -110,11 +110,11 @@ def test_parse_nws_alerts_extracts_references():
 # ---------------------------------------------------------------------------
 # 4. weather_client_base.py lines 912-924: _launch_enrichment_tasks auto-mode
 #    These lines are inside `if self.data_source == "auto":` and create tasks
-#    for sunrise_sunset, nws_discussion, vc_alerts, and vc_moon_data.
+#    for sunrise_sunset, nws_discussion, vc_alerts, vc_moon_data, and marine.
 # ---------------------------------------------------------------------------
 @pytest.mark.asyncio
 async def test_launch_enrichment_tasks_auto_mode_creates_smart_tasks():
-    """_launch_enrichment_tasks with data_source='auto' creates all four smart enrichment tasks."""
+    """_launch_enrichment_tasks with data_source='auto' creates all smart enrichment tasks."""
     import asyncio
 
     import accessiweather.weather_client_enrichment as enrichment
@@ -135,6 +135,7 @@ async def _noop(*args, **kwargs):
         patch.object(enrichment, "enrich_with_visual_crossing_moon_data", side_effect=_noop),
         patch.object(enrichment, "populate_environmental_metrics", side_effect=_noop),
         patch.object(enrichment, "enrich_with_aviation_data", side_effect=_noop),
+        patch.object(enrichment, "enrich_with_marine_data", side_effect=_noop),
     ):
         tasks = client._launch_enrichment_tasks(weather_data, location)
         # Cancel tasks to prevent ResourceWarning about pending coroutines
@@ -148,6 +149,7 @@ async def _noop(*args, **kwargs):
     assert "vc_moon_data" in tasks
     assert "environmental" in tasks
     assert "aviation" in tasks
+    assert "marine" in tasks
 
 
 @pytest.mark.asyncio
@@ -169,6 +171,7 @@ async def _noop(*args, **kwargs):
     with (
         patch.object(enrichment, "populate_environmental_metrics", side_effect=_noop),
         patch.object(enrichment, "enrich_with_aviation_data", side_effect=_noop),
+        patch.object(enrichment, "enrich_with_marine_data", side_effect=_noop),
     ):
         tasks = client._launch_enrichment_tasks(weather_data, location)
         for t in tasks.values():
@@ -181,3 +184,4 @@ async def _noop(*args, **kwargs):
     assert "vc_moon_data" not in tasks
     assert "environmental" in tasks
     assert "aviation" in tasks
+    assert "marine" in tasks
diff --git a/tests/test_hourly_forecast_presentation.py b/tests/test_hourly_forecast_presentation.py
index 5078a4af..fb3c2190 100644
--- a/tests/test_hourly_forecast_presentation.py
+++ b/tests/test_hourly_forecast_presentation.py
@@ -15,6 +15,8 @@
     HourlyForecast,
     HourlyForecastPeriod,
     Location,
+    MarineForecast,
+    MarineForecastPeriod,
 )
 from accessiweather.utils import TemperatureUnit
 
@@ -115,3 +117,48 @@ def test_build_forecast_exposes_daily_and_hourly_sections():
     assert "Hourly outlook: Clear through mid afternoon." in result.hourly_section_text
     assert "Next 1 Hours:" in result.hourly_section_text
     assert result.fallback_text == (f"{result.daily_section_text}\n\n{result.hourly_section_text}")
+
+
+def test_build_forecast_includes_marine_section_in_fallback_text():
+    forecast = Forecast(
+        periods=[
+            ForecastPeriod(
+                name="Today",
+                temperature=70.0,
+                temperature_low=54.0,
+                temperature_unit="F",
+                short_forecast="Sunny",
+            )
+        ]
+    )
+    marine = MarineForecast(
+        zone_id="ANZ530",
+        zone_name="Chesapeake Bay from Pooles Island to Sandy Point",
+        forecast_summary="South winds 10 to 15 knots with waves 1 to 2 feet.",
+        highlights=["South winds 10 to 15 knots", "Waves 1 to 2 feet"],
+        periods=[
+            MarineForecastPeriod(
+                name="Tonight",
+                summary="South winds 10 to 15 knots with waves 1 to 2 feet.",
+            )
+        ],
+    )
+
+    result = build_forecast(
+        forecast,
+        None,
+        Location(name="Annapolis", latitude=38.9784, longitude=-76.4922, marine_mode=True),
+        TemperatureUnit.FAHRENHEIT,
+        settings=AppSettings(),
+        marine=marine,
+    )
+
+    assert result.marine_summary == marine.forecast_summary
+    assert result.marine_highlights == marine.highlights
+    assert "Marine conditions for Annapolis:" in result.marine_section_text
+    assert (
+        "Marine zone: Chesapeake Bay from Pooles Island to Sandy Point (ANZ530)"
+        in result.marine_section_text
+    )
+    assert "Wind and wave highlights:" in result.marine_section_text
+    assert result.fallback_text == (f"{result.daily_section_text}\n\n{result.marine_section_text}")
diff --git a/tests/test_html_formatters.py b/tests/test_html_formatters.py
index 9029d273..c8b572e7 100644
--- a/tests/test_html_formatters.py
+++ b/tests/test_html_formatters.py
@@ -231,6 +231,27 @@ def test_with_generated_at(self):
         assert "Forecast generated: 2026-02-14 02:00 UTC" in html
         assert "generated-at" in html
 
+    def test_with_marine_section(self):
+        pres = ForecastPresentation(
+            title="Forecast",
+            marine_section_text=(
+                "Marine conditions for Annapolis:\n"
+                "Marine zone: Chesapeake Bay (ANZ530)\n"
+                "Summary: South winds 10 to 15 knots with waves 1 to 2 feet.\n"
+                "Wind and wave highlights:\n"
+                "  • South winds 10 to 15 knots\n"
+                "Tonight: South winds 10 to 15 knots with waves 1 to 2 feet."
+            ),
+            marine_summary="South winds 10 to 15 knots with waves 1 to 2 feet.",
+            marine_highlights=["South winds 10 to 15 knots", "Waves 1 to 2 feet"],
+        )
+        html = generate_forecast_html(pres)
+        assert 'aria-label="Marine forecast"' in html
+        assert "Marine Forecast" in html
+        assert "Marine Highlights" in html
+        assert "South winds 10 to 15 knots" in html
+        assert "Tonight: South winds 10 to 15 knots with waves 1 to 2 feet." in html
+
     def test_no_generated_at(self):
         pres = ForecastPresentation(title="F")
         html = generate_forecast_html(pres)
diff --git a/tests/test_main_window_forecast_sections.py b/tests/test_main_window_forecast_sections.py
index a832136a..ee12fe5c 100644
--- a/tests/test_main_window_forecast_sections.py
+++ b/tests/test_main_window_forecast_sections.py
@@ -64,3 +64,23 @@ def test_set_forecast_sections_updates_both_controls():
 
     win.daily_forecast_display.SetValue.assert_called_with("Daily text")
     win.hourly_forecast_display.SetValue.assert_called_with("Hourly text")
+
+
+def test_on_weather_data_received_appends_marine_to_daily_forecast_section():
+    win = _make_window()
+    win.app.presenter.present.return_value.forecast = ForecastPresentation(
+        title="Forecast",
+        fallback_text="Combined forecast",
+        daily_section_text="Daily section",
+        marine_section_text="Marine section",
+        hourly_section_text="Hourly section",
+    )
+
+    weather_data = MagicMock()
+    weather_data.alerts = None
+    weather_data.alert_lifecycle_diff = None
+
+    win._on_weather_data_received(weather_data)
+
+    win.daily_forecast_display.SetValue.assert_called_once_with("Daily section\n\nMarine section")
+    win.hourly_forecast_display.SetValue.assert_called_once_with("Hourly section")
diff --git a/tests/test_marine_enrichment.py b/tests/test_marine_enrichment.py
new file mode 100644
index 00000000..6f2b8423
--- /dev/null
+++ b/tests/test_marine_enrichment.py
@@ -0,0 +1,196 @@
+"""Tests for marine enrichment helpers and marine mode NWS enrichment."""
+
+from __future__ import annotations
+
+from unittest.mock import AsyncMock, MagicMock, patch
+
+import pytest
+
+from accessiweather.models import Location, WeatherAlert, WeatherAlerts, WeatherData
+from accessiweather.weather_client_enrichment import (
+    _build_marine_highlights,
+    _parse_marine_issued_at,
+    enrich_with_marine_data,
+)
+
+
+class _MockResponse:
+    def __init__(self, payload: dict):
+        self._payload = payload
+
+    def raise_for_status(self) -> None:
+        return None
+
+    def json(self) -> dict:
+        return self._payload
+
+
+def test_build_marine_highlights_deduplicates_and_limits_results():
+    periods = [
+        {
+            "shortForecast": "South winds 10 to 15 knots. Waves 1 to 2 feet.",
+            "detailedForecast": "South winds 10 to 15 knots. Seas around 2 feet.",
+        },
+        {
+            "shortForecast": "Gusts up to 20 knots. Swells 3 feet.",
+            "detailedForecast": "Gusts up to 20 knots. Swells 3 feet.",
+        },
+        {"shortForecast": "North winds 5 knots.", "detailedForecast": ""},
+    ]
+
+    highlights = _build_marine_highlights(periods)
+
+    assert highlights == [
+        "South winds 10 to 15 knots",
+        "Waves 1 to 2 feet",
+        "Seas around 2 feet",
+        "Gusts up to 20 knots",
+    ]
+
+
+@pytest.mark.parametrize(
+    ("value", "expected_none"),
+    [
+        ("2026-03-27T15:00:00Z", False),
+        ("not-a-date", True),
+        (None, True),
+    ],
+)
+def test_parse_marine_issued_at_handles_valid_and_invalid_values(value, expected_none):
+    result = _parse_marine_issued_at(value)
+
+    assert (result is None) is expected_none
+
+
+@pytest.mark.asyncio
+async def test_enrich_with_marine_data_noops_when_marine_mode_disabled():
+    location = Location(name="Inland", latitude=39.0, longitude=-76.0, marine_mode=False)
+    weather_data = WeatherData(location=location)
+    client = MagicMock()
+    client._is_us_location.return_value = True
+
+    await enrich_with_marine_data(client, weather_data, location)
+
+    client._get_http_client.assert_not_called()
+    assert weather_data.marine is None
+
+
+@pytest.mark.asyncio
+async def test_enrich_with_marine_data_populates_forecast_and_merges_alerts():
+    location = Location(name="Annapolis", latitude=38.9784, longitude=-76.4922, marine_mode=True)
+    weather_data = WeatherData(
+        location=location,
+        alerts=WeatherAlerts(
+            alerts=[
+                WeatherAlert(
+                    id="existing-alert",
+                    title="Existing Advisory",
+                    description="Existing advisory",
+                )
+            ]
+        ),
+    )
+
+    client = MagicMock()
+    client._is_us_location.return_value = True
+    client._get_http_client.return_value = object()
+    client.user_agent = "AccessiWeather Test"
+    client.nws_base_url = "https://api.weather.gov"
+    client.timeout = 30
+
+    zone_response = _MockResponse(
+        {
+            "features": [
+                {
+                    "id": "ANZ530",
+                    "properties": {
+                        "id": "ANZ530",
+                        "name": "Chesapeake Bay from Pooles Island to Sandy Point",
+                    },
+                }
+            ]
+        }
+    )
+    alerts_response = _MockResponse({"features": []})
+    marine_forecast = {
+        "properties": {
+            "name": "Chesapeake Bay from Pooles Island to Sandy Point",
+            "updateTime": "2026-03-27T15:00:00Z",
+            "periods": [
+                {
+                    "name": "Tonight",
+                    "shortForecast": "South winds 10 to 15 knots. Waves 1 to 2 feet.",
+                    "detailedForecast": "South winds 10 to 15 knots. Waves 1 to 2 feet.",
+                },
+                {
+                    "name": "Saturday",
+                    "shortForecast": "Gusts up to 20 knots.",
+                    "detailedForecast": "Gusts up to 20 knots. Seas around 2 feet.",
+                },
+            ],
+        }
+    }
+    marine_alert = WeatherAlert(
+        id="marine-alert",
+        title="Small Craft Advisory",
+        description="Hazardous conditions expected.",
+        source="NWS",
+    )
+
+    with (
+        patch(
+            "accessiweather.weather_client_enrichment.nws_client._client_get",
+            new=AsyncMock(side_effect=[zone_response, alerts_response]),
+        ),
+        patch(
+            "accessiweather.weather_client_enrichment.nws_client.get_nws_marine_forecast",
+            new=AsyncMock(return_value=marine_forecast),
+        ),
+        patch(
+            "accessiweather.weather_client_enrichment.nws_client.parse_nws_alerts",
+            return_value=WeatherAlerts(alerts=[marine_alert]),
+        ),
+    ):
+        await enrich_with_marine_data(client, weather_data, location)
+
+    assert weather_data.marine is not None
+    assert weather_data.marine.zone_id == "ANZ530"
+    assert weather_data.marine.zone_name == "Chesapeake Bay from Pooles Island to Sandy Point"
+    assert weather_data.marine.forecast_summary == "South winds 10 to 15 knots. Waves 1 to 2 feet."
+    assert weather_data.marine.issued_at is not None
+    assert len(weather_data.marine.periods) == 2
+    assert weather_data.marine.highlights == [
+        "South winds 10 to 15 knots",
+        "Waves 1 to 2 feet",
+        "Gusts up to 20 knots",
+        "Seas around 2 feet",
+    ]
+    assert weather_data.alerts is not None
+    assert sorted(alert.id for alert in weather_data.alerts.alerts) == [
+        "existing-alert",
+        "marine-alert",
+    ]
+    merged_marine_alert = next(
+        alert for alert in weather_data.alerts.alerts if alert.id == "marine-alert"
+    )
+    assert merged_marine_alert.source == "NWS Marine"
+
+
+@pytest.mark.asyncio
+async def test_enrich_with_marine_data_returns_cleanly_when_no_zone_found():
+    location = Location(name="Annapolis", latitude=38.9784, longitude=-76.4922, marine_mode=True)
+    weather_data = WeatherData(location=location)
+    client = MagicMock()
+    client._is_us_location.return_value = True
+    client._get_http_client.return_value = object()
+    client.user_agent = "AccessiWeather Test"
+    client.nws_base_url = "https://api.weather.gov"
+
+    with patch(
+        "accessiweather.weather_client_enrichment.nws_client._client_get",
+        new=AsyncMock(return_value=_MockResponse({"features": []})),
+    ):
+        await enrich_with_marine_data(client, weather_data, location)
+
+    assert weather_data.marine is None
+    assert weather_data.alerts is None
diff --git a/tests/test_models.py b/tests/test_models.py
index 55ca186e..46d3dcfe 100644
--- a/tests/test_models.py
+++ b/tests/test_models.py
@@ -17,6 +17,8 @@
     HourlyForecast,
     HourlyForecastPeriod,
     Location,
+    MarineForecast,
+    MarineForecastPeriod,
     MinutelyPrecipitationForecast,
     MinutelyPrecipitationPoint,
     WeatherAlert,
@@ -359,6 +361,20 @@ def test_has_any_data(self):
         )
         assert with_minutely.has_any_data() is True
 
+        with_marine = WeatherData(
+            location=loc,
+            marine=MarineForecast(
+                zone_id="ANZ530",
+                periods=[
+                    MarineForecastPeriod(
+                        name="Tonight",
+                        summary="South winds 10 to 15 knots with waves 1 to 2 feet.",
+                    )
+                ],
+            ),
+        )
+        assert with_marine.has_any_data() is True
+
 
 class TestAppSettings:
     """Tests for AppSettings model."""