Seminole-Mary Lake
Seminole-Mary Lake in Seminole County, Florida has a water quality grade of B (Good). Water clarity: 5.5 ft visibility. Phosphorus: 17 µg/L.
- Clarity
- 5.5 ft
- Max depth
- ~37 ft est.
- Type
- Mesotrophic
- Trend
- ↓ Declining
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Seminole-Mary Lake is a mesotrophic lake in Seminole County, Florida with an estimated average depth of about 37 feet. Water quality is graded B based on 1 sampling years through 2025. Overall water quality is declining over recent sampling years. Compared to the 121 other monitored lakes in Seminole County, Seminole-Mary Lake ranks #37 for water quality.
Source: EPA Water Quality Portal sampling records, FDEP, last sampled 2025-02-28. Grade methodology: LakeQuality methodology.
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Swimming Safety
Grade onlyLow algae
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Good for swimming, clear water with low algae levels
Water Quality Grade: B (Good)
Murky, only visible to about 5.5 ft. Phosphorus level: 17 µg/L. Trophic State Index: 49.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 5.5 ft | Not graded |
| Phosphorus | 17 µg/L | Good |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 49 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Seminole-Mary Lake
Compare lakeside cabins, hotels, and vacation rentals near Seminole-Mary Lake in Seminole County, Florida — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
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Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~37 ft est. |
| Average Depth | ~10 ft est. |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Florida has not published bathymetry for Seminole-Mary Lake.
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Fishing Seminole-Mary Lake
Water Quality Trend: ↓ Declining
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.49 m/yr | 5 |
| Phosphorus | ↓ Declining | +0.9 µg/L/yr | 5 |
EPA Impairment Status
Seminole-Mary Lake is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit FL2973G · Official waterbody report · Matched by proximity (2.95 km)
County Ranking
Ranked #37 of 122 lakes in Seminole County
Nearby Lakes in Seminole County
Frequently asked questions about Seminole-Mary Lake
Where is Seminole-Mary Lake?
- Seminole-Mary Lake is a lake in Seminole County, Florida. LakeQuality grades it B for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Seminole-Mary Lake?
- Seminole-Mary Lake in Seminole County, Florida has a water quality grade of B (Good). Water clarity: 5.5 ft visibility. Phosphorus: 17 µg/L.
Is Seminole-Mary Lake safe to swim in?
- Good for swimming, clear water with low algae levels. Seminole-Mary Lake has a water quality grade of B (Good). Always check local health department advisories before swimming.
How deep is Seminole-Mary Lake?
- No published bathymetric survey covers Seminole-Mary Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 37 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Explore Seminole-Mary Lake across LakeQuality
Planning a trip around Canaveral?
Seminole-Mary Lake is about 34 miles from Canaveral National Seashore. Crowds there swing hard by season, so the month you pick changes both how busy the park is and what lodging costs.
Best time to visit Canaveral →More Florida Lake Rankings
Other Grade B Lakes in Florida
Mesotrophic Lakes in Florida
Where this data comes from
197 measurements from 3 monitoring stations, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- FLORIDA LAKEWATCH
21FLKWAT_WQX197 samples · 2020–2025
Monitoring station identifiers (3)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)