What is the water quality grade for Seminole-Mary Lake?

Seminole-Mary Lake in Seminole County, Florida received 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 an overall water quality grade of B. Always check local health department advisories before swimming.

Seminole-Mary Lake

Seminole County, FloridaMesotrophic

Seminole-Mary Lake is a mesotrophic lake in Seminole County, Florida. Water quality is graded B based on 2 sampling years through 2025. Compared to the 167 other monitored lakes in Seminole County, Seminole-Mary Lake ranks #39 for water quality.

Source: EPA Water Quality Portal sampling records, Florida DNR, last sampled 2025-02-28. Grade methodology: LakeGrade methodology.

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Swimming Safety

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	C
Phosphorus	17 µg/L	B
Chlorophyll-a (Algae)	No data
Trophic State Index (TSI)	49	Mesotrophic

Moderate nutrients, good water quality

Location

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County Ranking

Ranked #39 of 168 lakes in Seminole County

Cleaner Lakes Within 30 Miles

Seminole-Mary Lake holds Grade B. 2 nearby lakes hold higher grades.

See full comparison →

Nearby Lakes in Seminole County

Seminole-Little Mary Lake

Seminole County

East Crystal Lake

Seminole County

East Crystal Lake @ Center

Seminole County

Seminole-West Crystal Lake

More Florida Lake Rankings

Cleanest lakes in Florida

Top 25 by overall water quality score

Best swimming lakes in Florida

Grade A/B + low algae filter

Family fishing lakes in Florida

Panfish-rich, public access

All Florida lakes

Full state directory

Other Grade B Lakes in Florida

Bay-Deer Point Lake

Bay County · Clarity: 4 ft

Brevard-Clear Lake

Brevard County · Clarity: 9.8 ft

Alachua-Santa Fe Painter Canal Lake

Alachua County · Clarity: 5.5 ft

Marion-Deerback Lake

Marion County · Clarity: 7 ft

Hillsborough-Flynn Lake

Hillsborough County · Clarity: 6 ft

Western Lake Middle

Walton County · Clarity: 4 ft

Mesotrophic Lakes in Florida

Bay-Deer Point Lake Brevard-Clear Lake Marion-Deerback Lake Hillsborough-Flynn Lake

Lake Size & Watershed

Watershed (drainage) area

1 sq mi

Surface area

77 acres

Mean depth (est.)

9.5 ft

Shoreline

2.6 mi

Elevation

49 ft

Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.

Data Sources

Water quality data from the EPA Water Quality Portal

Lake size & watershed from HydroLAKES (HydroSHEDS)

Grading methodology based on Metropolitan Council standards

Most recent sample: 2025-02-28

Monitoring stations: 3

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