Lake Marion
Lake Marion in Seminole County, Florida has a water quality grade of B (Good). Water clarity: 2 ft visibility. Phosphorus: 38 µg/L.
- Clarity
- 2 ft
- Typical in July
- 89°F
- Type
- Eutrophic
- Trend
- ↓ Declining
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Lake Marion is a productive, nutrient-rich eutrophic lake in Seminole County, Florida. 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, Lake Marion ranks #60 for water quality.
Source: EPA Water Quality Portal sampling records, FDEP, last sampled 2025-07-01. Grade methodology: LakeQuality methodology.
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Swimming Safety
Grade onlyLimited data
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)
Very murky, less than 2 ft of visibility. Phosphorus level: 38 µg/L. Trophic State Index: 62.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2 ft | Not graded |
| Phosphorus | 38 µg/L | Good |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 62 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Lake Marion
Compare lakeside cabins, hotels, and vacation rentals near Lake Marion 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.
Top-rated places to stay near Lake Marion
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Florida’s top lakes →
Water Temperature
Lake Marion typically sits around 89°F at the surface in July. Summer average is about 89°F. Usually warmest in Jul (about 89°F) and coldest in Jan (about 66°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 58 field readings (2010–2025) via the EPA Water Quality Portal. See the full Lake Marion water temperature breakdown →
Fishing Lake Marion
Water Quality Trend: ↓ Declining
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.087 m/yr | 6 |
| Phosphorus | → Stable | +0.57 µg/L/yr | 6 |
EPA Impairment Status
Lake Marion 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 FL2998D · Official waterbody report
County Ranking
Ranked #60 of 122 lakes in Seminole County
Nearby Lakes in Seminole County
Frequently asked questions about Lake Marion
Where is Lake Marion?
- Lake Marion 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 Lake Marion?
- Lake Marion in Seminole County, Florida has a water quality grade of B (Good). Water clarity: 2 ft visibility. Phosphorus: 38 µg/L.
Is Lake Marion safe to swim in?
- Good for swimming, clear water with low algae levels. Lake Marion has a water quality grade of B (Good). Always check local health department advisories before swimming.
What is the water temperature of Lake Marion?
- Lake Marion typically sits around 89°F at the surface in July, from 58 EPA Water Quality Portal field readings (2010–2025). That is a typical value for the month, not a live reading.
Explore Lake Marion across LakeQuality
Planning a trip around Canaveral?
Lake Marion is about 38 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
Eutrophic Lakes in Florida
Where this data comes from
43 measurements from 1 monitoring station, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Submitting organization not recorded for these samples43 samples · 2020–2025
Monitoring station identifiers (1)
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