Serpent Lake
Crow Wing County, Minnesota1,116 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Serpent Lake. Here is what has been measured.
- Oligotrophic
- Impaired · Mercury
- zebra mussel
- 65 ft max depth
- Public access
Serpent Lake in Crow Wing County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 25 ft visibility. Phosphorus: 12 µg/L. Chlorophyll-a (algae): 1.6 µg/L. Maximum depth: 65 ft. Surface area: 1116.34 acres.
Minnesota DNR's Targeted Survey on August 21, 2023 caught 3.67 walleye per gill net at Serpent Lake. DNR survey details →
Free interactive depth-contour map of Serpent Lake, reaching a maximum surveyed depth of 60 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Minnesota DNR.
Serpent Lake is a 1,116-acre cold, clear oligotrophic lake in Crow Wing County, Minnesota with a maximum depth of 65 feet. The lake supports 17 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 1 public boat landing. Compared to the 84 other monitored lakes in Crow Wing County, Serpent Lake ranks #25 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-17. Methodology: how these readings are compared.
Serpent Lake covers about 1,100 acres in Crow Wing County. It has one public boat landing. The median ice-out date is April 15, which is when the open-water season begins. For a place on the water, look through cabin and lake-house rentals near Serpent Lake on Vrbo. For a hotel or motel room, Booking.com and Expedia both search around the lake.
What Serpent Lake is good for
From access and monitoring records, not editorial picks.
- Clear water25 ft of visibility
- Boat launch1 documented ramp
- Fishing17 species recorded
- Ice seasonIce-out around Apr 15
- Deep water65 ft surveyed max depth
- Big water1,116 acres
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. Serpent Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Whether Serpent Lake is safe to swim in today is a call for the Minnesota Pollution Control Agency and the Minnesota DNR and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Serpent Lake
These are the measurements Minnesota PCA publishes for Serpent 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 25 ft down. Phosphorus 12 µg/L. Chlorophyll-a 1.6 µg/L. TSI 35.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 25ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 12µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 1.6µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 35 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Serpent Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Serpent Lake typically sits around 63°F at the surface in September. Summer average is about 66°F. Usually warmest in Jul (about 68°F) and coldest in May (about 50°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (50°F) to its warmest (68°F).
Typical surface water temperature by month, from 194 field readings (2011–2025) via the EPA Water Quality Portal. See the full Serpent Lake water temperature breakdown →
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Serpent Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was moderate (26,546 cells/mL) on November 22, 2025.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Minnesota DNR's Targeted Survey on August 21, 2023 caught 3.67 walleye per gill net at Serpent Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Serpent Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is stable. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
11 surveys on file from MN DNR Fisheries. Most recent: 2023-08-21 (Targeted Survey).
11 surveys on file · most recent 2023-08-21 (Targeted Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Bluntnose Minnow | 67.90 | ||
| Largemouth Bass | 13.69 | 5–17 in 2023-08-21 | 0.68 lb |
| Bluegill | 12.03 | 3–8 in 2023-08-21 | 0.14 lb |
CPUE = catch per unit effort, fish caught per net per set in a standardised survey. It measures abundance, not size, and is not a weekly bite report.
Length Distributions
Number of fish caught at each inch class in the most recent survey that recorded lengths. Red dashed line marks an approximate trophy threshold for that species.
Largemouth Bass
Bluegill
From the 2023-08-21 survey
Serpent Lake is a 1,057-acre lake located in Crow Wing County. It spans the cities of Crosby on the west shore and Deerwood on the east. A public access is located in the Crosby city park on the west end. Another access is located just north of Deerwood on the east shore. Serpent reaches depths of 65' with 32% of the…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Serpent Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — SerpentFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Serpent (0012)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — SerpentFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — SerpentPublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
65 ft
Surface area
1,116 acres
Shoreline
9 mi
Littoral zone
30%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
12 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,234 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Serpent Lake (West)Public
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Serpent Lake
Compare lakeside cabins, hotels, and vacation rentals near Serpent Lake in Crow Wing County, Minnesota — 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 Serpent Lake
Prices for Oct 9–11, 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 Minnesota’s top lakes →
Follow Serpent Lake’s readings
Email me when new measurements post for this lake. Updates stay free.
Or email
Fish Species
Click a species to see every lake where it is documented.
Fishing Serpent 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: Stable
Based on 6 years of monitoring (2020–2025).
Water clarity
Stable6 years
Phosphorus
Stable-0.16 µg/L/yr6 years
Chlorophyll-a
Stable-0.04 µg/L/yr6 years
Ice season
Typical ice-out
Apr 15
Earliest Mar 15, 2024 · Latest May 5, 2022
Typical ice-in
Dec 4
Earliest Nov 20, 2018 · Latest Jan 5, 2024
Most recent ice-out
Apr 15
2025
19 observations · Minnesota PCA ice records
EPA Impairment Status
Serpent Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
Designated uses not supporting: Fish consumption.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN18-0090-00 · Official waterbody report
Nearby Lakes in Crow Wing County
Frequently asked questions about Serpent Lake
Where is Serpent Lake?
- Serpent Lake is a lake in Crow Wing County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Serpent Lake?
- Serpent Lake in Crow Wing County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 25 ft visibility. Phosphorus: 12 µg/L. Chlorophyll-a (algae): 1.6 µg/L. Maximum depth: 65 ft. Surface area: 1116.34 acres.
Is Serpent Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Serpent Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
What is the water temperature of Serpent Lake?
- Serpent Lake typically sits around 63°F at the surface in September, from 194 EPA Water Quality Portal field readings (2011–2025). That is a typical value for the month, not a live reading.
How deep is Serpent Lake?
- Serpent Lake has a maximum depth of 65 feet. The lake covers 1116.34 acres.
What fish are in Serpent Lake?
- Fish species found in Serpent Lake include black bullhead, black crappie, bluegill, bowfin (dogfish), brown bullhead, burbot, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, rock bass, smallmouth bass, tullibee (cisco), walleye, white sucker, yellow bullhead, yellow perch. Serpent Lake is located in Crow Wing County, Minnesota.
What did the DNR fisheries survey find at Serpent Lake?
- Minnesota DNR's Targeted Survey on August 21, 2023 caught 3.67 walleye per gill net at Serpent Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Serpent Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is stable. Catch rate is not a swim clearance and is not a weekly bite report.
When does Serpent Lake thaw?
- Serpent Lake typically has ice-out around Apr 15. Ice typically forms around Dec 4. The open water season is approximately 233 days.
Does Serpent Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Serpent Lake (clouds, ice, or an off-season gap). The most recent reading was moderate (26,546 cells/mL). Blue-green algae can appear and clear within days, so check Minnesota's current advisory before swimming.
Are there boat ramps on Serpent Lake?
- Serpent Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Serpent Lake (West). Public access is listed as yes.
Can I fish at Serpent Lake?
- Serpent 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 Minnesota's fish and wildlife agency, so check its current regulations before you go.
Explore Serpent Lake across LakeQuality
Depth, room, public access, and the state wake-sport rules
Fish species and the cleanest lakes across Minnesota
Fish species and best lakes in Crow Wing County
Species activity outlook by water temperature and season
Top lakes and where to stay in the Brainerd Lakes area
Top lakes and where to stay in the Mille Lacs Area area
Where to stay at Minnesota's top lakes, each with its readings
Lakes in the Pine River Watersheds (Brainerd Lakes), ranked by water quality
Minnesota's cleanest lakes, ranked on agency measurements
More lakes in Minnesota
State Parks Near Serpent Lake
Other Lakes in Minnesota
Oligotrophic Lakes in Minnesota
Compare Serpent Lake With Nearby Lakes
Where this data comes from
125 measurements from 2 monitoring stations, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA125 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
Monitoring station identifiers (2)
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
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory
Ice data from Minnesota DNR Climate