Alligator Lake
Alligator Lake in Pinellas County, Florida has a water quality grade of D (Nutrient-rich). Water clarity: 2.6 ft visibility. Phosphorus: 155 µg/L. Surface area: 79 acres.
- Clarity
- 2.6 ft
- Typical in August
- 87°F
- Area
- 79 acres
- Type
- Hypereutrophic
- Trend
- ↓ Declining
- Public access
- Yes
Grade D measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near Alligator Lake →
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Alligator Lake is a 79-acre highly nutrient-loaded hypereutrophic lake in Pinellas County, Florida. Water quality is graded D based on 1 sampling years through 2025. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 33 other monitored lakes in Pinellas County, Alligator Lake ranks #14 for water quality.
Source: EPA Water Quality Portal sampling records, FDEP, last sampled 2025-01-29. Grade methodology: LakeQuality methodology.
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Swimming Safety
Grade onlyBacteria D
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.
Based on E. coli testing, Alligator Lake frequently exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 14.5% of 55 samples across 8 seasons.
This is a historical summary of past testing, not a current condition — bacteria levels change quickly, especially after rain. Always check Florida’s current beach and health-department advisories before swimming.
Water Quality Grade: D (Nutrient-rich)
Very murky, less than 2.6 ft of visibility. Phosphorus level: 155 µg/L. Trophic State Index: 70.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.6 ft | Not graded |
| Phosphorus | 155 µg/L | Poor |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 70 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Where to stay near Alligator Lake
Compare lakeside cabins, hotels, and vacation rentals near Alligator Lake in Pinellas 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. The water-quality grade measures nutrients and algae, not lodging — cabins and rentals around Alligator Lake are listed below.
Top-rated places to stay near Alligator Lake
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Planning a whole trip? See where to stay at Florida’s top lakes →
Water Temperature
Alligator Lake typically sits around 87°F at the surface in August. Summer average is about 86°F. Usually warmest in Jun (about 87°F) and coldest in Jan (about 60°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 325 field readings (2010–2025) via the EPA Water Quality Portal. See the full Alligator Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 79 acres |
| Public Access | Yes |
No bathymetric survey has been published for Alligator Lake, so its depth is not documented here.
Recreation & Access
- Safety Harbor MarinaPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Alligator Lake
Water Quality Trend: ↓ Declining
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.059 m/yr | 5 |
| Phosphorus | ↓ Declining | +12.5 µg/L/yr | 5 |
Reservoir Info (USACE NID)
Alligator Lake is a man-made reservoir impounded by the Alligator Lake Weir, built primarily for flood risk reduction on the Alligator Creek; earth-type dam, 9 ft tall and 103 ft long.
- Surface area
- 79 ac
- Normal storage
- 200 ac-ft
- Max storage
- 311 ac-ft
- Drainage area
- 8 sq mi
- Hazard class
- Significant
- Owner
- PINELLAS COUNTY
All listed purposes: Flood Risk Reduction;Recreation;Water Supply.
Source: USACE National Inventory of Dams, NID ID FL78002 · Operator website · Matched by proximity (0.01 km)
EPA Impairment Status
Alligator 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 FL1574A · Official waterbody report
County Ranking
Ranked #14 of 34 lakes in Pinellas County
Nearby Lakes With Higher Grades
Alligator Lake holds Grade D. One nearby lake has a higher nutrient-and-algae grade — useful for a swim day, not a reason to skip lodging here.
See full comparison →Nearby Lakes in Pinellas County
Frequently asked questions about Alligator Lake
Where is Alligator Lake?
- Alligator Lake is a lake in Pinellas County, Florida. LakeQuality grades it D for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Alligator Lake?
- Alligator Lake in Pinellas County, Florida has a water quality grade of D (Nutrient-rich). Water clarity: 2.6 ft visibility. Phosphorus: 155 µg/L. Surface area: 79 acres.
Is Alligator Lake safe to swim in?
- Based on E. coli testing, Alligator Lake frequently exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 14.5% of 55 samples across 8 seasons. That works out to a bacteria swim-safety grade of D — a historical summary of past testing, not a current reading. Alligator Lake has a water quality grade of D (Nutrient-rich). Bacteria levels can spike quickly after heavy rain, so always check Florida's current beach and health-department advisories before you swim.
What is the water temperature of Alligator Lake?
- Alligator Lake typically sits around 87°F at the surface in August, from 325 EPA Water Quality Portal field readings (2010–2025). That is a typical value for the month, not a live reading.
Are there boat ramps on Alligator Lake?
- Alligator Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Safety Harbor Marina. Public access is listed as yes.
Explore Alligator Lake across LakeQuality
More Florida Lake Rankings
Other Grade D Lakes in Florida
Hillsborough County · 2.4 ft
Pasco County · 1 ft
Hillsborough County · Nutrient-rich
Hillsborough County · 2.5 ft
Hillsborough County · 2 ft
Hillsborough County · Nutrient-rich
Hypereutrophic Lakes in Florida
Where this data comes from
77 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 samples77 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
Named boat-access points from the USGS National Boat Ramps inventory