Where is Saint Marys Lake?

Saint Marys Lake is a lake in St. Mary's County, Maryland. Its water-quality measurements are published by MDE and shown on this page as reported.

How deep is Saint Marys Lake?

Saint Marys Lake has a maximum depth of 24 feet. The lake covers 226 acres.

Are there boat ramps on Saint Marys Lake?

Saint Marys Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include St. Mary's River State Park. Public access is listed as yes.

Can I fish at Saint Marys Lake?

Saint Marys 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 Maryland's fish and wildlife agency, so check its current regulations before you go.

Saint Marys Lake

St. Mary's County, Maryland226 acresView map Directions

No nutrient or algae sampling on record from MDE for this lake.

Max depth

24 ft

Bathymetric survey

Area

226 acres

Surface area

Shoreline

6.5 mi

Measured length

Impaired · Mercury
24 ft max depth
Public access

See the measurements Directions Where to stay

Saint Marys Lake in St. Mary's County, Maryland has water-quality measurements published by MDE, shown here as reported. Maximum depth: 24 ft. Surface area: 226 acres.

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Saint Marys Lake is a 226-acre lake in St. Mary's County, Maryland with a maximum depth of 24 feet. Limited fish-species data available. Public access is available with 1 public boat landing.

Source: EPA Water Quality Portal sampling records, your state environmental agency. Methodology: how these readings are compared.

What Saint Marys Lake is good for

From access and monitoring records, not editorial picks.

Boat launch1 documented ramp

Swimming conditions

No reading

Not rated

Nutrient and algae readings are not a swimming clearance. Saint Marys Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.

Whether Saint Marys Lake is safe to swim in today is a call for the Maryland Department of the Environment and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.

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Water quality measurements for Saint Marys Lake

These are the measurements MDE publishes for Saint Marys Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.

No clarity data. TSI undefined.

Ask about Saint Marys Lake

Answers come straight from the public measurements and survey records on this page.

Lake Details

Max depth

24 ft

Surface area

226 acres

Shoreline

6.5 mi

Public access

Yes

Listed by MDE

Recreation & Access

Boat Landings

Yes

Public Access

St. Mary's River State ParkPublic

Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps

Stays via Stay22

Stays near Saint Marys Lake

Compare lakeside cabins, hotels, and vacation rentals near Saint Marys Lake in St. Mary's County, Maryland — 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 Saint Marys Lake

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Fishing Saint Marys Lake

→ Saint Marys Lake fishing regulations (limits, seasons, special rules)

EPA Impairment Status

Saint Marys Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).

Causes of impairment

Mercury

Designated uses not supporting: Fish consumption.

A Total Maximum Daily Load (TMDL) plan has been approved.

Source: EPA ATTAINS assessment unit MD-021401030718-ST_MARYS_LAKE · Official waterbody report

Nearby Lakes in St. Mary's County

Green Holly Pond5.2 miView →Pond Number Three6.8 miView →Hall Pond—View →Cleve Branch Lake3 ft clear10.1 miView →Mill Creek Lake3 ft clear10.1 miView →Burrell Branch Lake3 ft clear10.1 miView →

Frequently asked questions about Saint Marys Lake

Where is Saint Marys Lake?: Saint Marys Lake is a lake in St. Mary's County, Maryland. Its water-quality measurements are published by MDE and shown on this page as reported.
What is the water quality of Saint Marys Lake?: Saint Marys Lake in St. Mary's County, Maryland has water-quality measurements published by MDE, shown here as reported. Maximum depth: 24 ft. Surface area: 226 acres.
Is Saint Marys Lake safe to swim in?: Nutrient and algae readings are not a swimming clearance. Saint Marys Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
How deep is Saint Marys Lake?: Saint Marys Lake has a maximum depth of 24 feet. The lake covers 226 acres.
Are there boat ramps on Saint Marys Lake?: Saint Marys Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include St. Mary's River State Park. Public access is listed as yes.
Can I fish at Saint Marys Lake?: Saint Marys 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 Maryland's fish and wildlife agency, so check its current regulations before you go.