Sea Lion Lake
Florence County, Wisconsin114 acresView mapDirections
Wisconsin DNR publishes the water-quality measurements for Sea Lion Lake. Here is what has been measured.
- Oligotrophic
- Zebra Mussel
- 82 ft max depth
- Public access
Sea Lion Lake in Florence County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 21 ft visibility. Phosphorus: 11.5 µg/L. Maximum depth: 82 ft. Surface area: 114 acres.
Wisconsin DNR rates Panfish as abundant on Sea Lion Lake. DNR survey details →
Sea Lion Lake is a 114-acre cold, clear oligotrophic lake in Florence County, Wisconsin with a maximum depth of 82 feet. Overall water quality is declining over recent sampling years. The lake supports 5 documented fish species including Panfish, Largemouth Bass, and Smallmouth Bass. Public access is available with 1 public boat landing. Compared to the 11 other monitored lakes in Florence County, Sea Lion Lake ranks #6 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-07-03. Methodology: how these readings are compared.
Sea Lion Lake covers about 110 acres in Florence County. It has one public boat landing. If you are planning to stay, you can search lake houses and cabins around Sea Lion Lake on Vrbo, or look for a hotel room near the lake on Booking.com or Expedia.
What Sea Lion Lake is good for
From access and monitoring records, not editorial picks.
- Clear water21 ft of visibility
- Boat launch1 documented ramp
- Fishing5 species recorded
- Deep water82 ft surveyed max depth
Swimming conditions
Readings onlyLow algae
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Sea Lion Lake is safe to swim in today is a call for the Wisconsin Department of Natural Resources and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Sea Lion Lake
These are the measurements Wisconsin DNR publishes for Sea Lion Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Crystal clear, you can see 21 ft down. Phosphorus 11.5 µg/L. TSI 36.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 21ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 11.5µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | No reading The green pigment in algae — a direct measure of how much algae is in the water. | |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 36 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Sea Lion Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Sea Lion Lake typically sits around 65°F at the surface in September. Summer average is about 74°F. Usually warmest in Jul (about 75°F) and coldest in May (about 59°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (59°F) to its warmest (75°F).
Typical surface water temperature by month, from 17 field readings (2024–2026) via the EPA Water Quality Portal. See the full Sea Lion Lake water temperature breakdown →
Wisconsin DNR rates Panfish as abundant on Sea Lion Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Sea Lion Lake’s water-quality measurements separately, and the water-quality trend over 7 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
WI DNR Lake Profile
Authoritative data from the Wisconsin DNR LakePages. Monitored by volunteers since 2020. 1 station on file (most recent sample 2025).
Fish Species (DNR-rated)
Lake Details
Max depth
82 ft
Surface area
114 acres
Public access
Yes
Listed by Wisconsin DNR
Recreation & Access
- Sea Lion LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Sea Lion Lake
Compare lakeside cabins, hotels, and vacation rentals near Sea Lion Lake in Florence County, Wisconsin — 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 Sea Lion Lake
Prices for Oct 16–18, 4 adults. Change dates on the map below.
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 Wisconsin’s top lakes →
Follow Sea Lion Lake’s readings
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Fish Species
Click a species to see every lake where it is documented.
Fishing Sea Lion Lake
Invasive & Introduced Species
Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.
Water Quality Trend: Worsening
Based on 7 years of monitoring (2020–2026).
Water clarity
Worsening7 years
Phosphorus
Worsening+3 µg/L/yr3 years
Nearby Lakes in Florence County
Frequently asked questions about Sea Lion Lake
Where is Sea Lion Lake?
- Sea Lion Lake is a lake in Florence County, Wisconsin. Its water-quality measurements are published by Wisconsin DNR and shown on this page as reported.
What is the water quality of Sea Lion Lake?
- Sea Lion Lake in Florence County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 21 ft visibility. Phosphorus: 11.5 µg/L. Maximum depth: 82 ft. Surface area: 114 acres.
Is Sea Lion Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Sea Lion Lake?
- Sea Lion Lake typically sits around 65°F at the surface in September, from 17 EPA Water Quality Portal field readings (2024–2026). That is a typical value for the month, not a live reading.
How deep is Sea Lion Lake?
- Sea Lion Lake has a maximum depth of 82 feet. The lake covers 114 acres.
What fish are in Sea Lion Lake?
- Fish species found in Sea Lion Lake include Panfish, Largemouth Bass, Smallmouth Bass, Northern Pike, Walleye. Sea Lion Lake is located in Florence County, Wisconsin.
What did the DNR fisheries survey find at Sea Lion Lake?
- Wisconsin DNR rates Panfish as abundant on Sea Lion Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Sea Lion Lake’s water-quality measurements separately, and the water-quality trend over 7 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
Are there boat ramps on Sea Lion Lake?
- Sea Lion Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Sea Lion Lake. Public access is listed as yes.
Can I fish at Sea Lion Lake?
- Sea Lion Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by Wisconsin's fish and wildlife agency, so check its current regulations before you go.
Explore Sea Lion Lake across LakeQuality
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Fish species and best lakes in Florence County
Species activity outlook by water temperature and season
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Wisconsin's cleanest lakes, ranked on agency measurements
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Oligotrophic Lakes in Wisconsin
Where this data comes from
44 measurements from 1 monitoring station, 2020–2026. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Wisconsin Department of Natural Resources
WIDNR_WQX44 samples · 2020–2026
Analytical methods
- Phosphorus by Colorimetry
Monitoring station identifiers (1)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Fish and recreation data from Wisconsin DNR Lakes
Named boat-access points from the USGS National Boat Ramps inventory