Shallow Lakes in Minnesota & Wisconsin
Lakes under 20 feet deep in Minnesota and Wisconsin ranked by water quality. Shallow lakes warm quickly in summer and are great for wading and family swimming, but are more susceptible to algae blooms and winter fish kills.
Maximum-depth data currently comes from the Minnesota and Wisconsin DNR lake surveys, so these rankings cover MN and WI lakes only. Grades for the other 10 covered states are based on clarity and nutrient measurements.
| Rank | Lake | County | State | Grade | Depth | Area | Fish |
|---|---|---|---|---|---|---|---|
| 1 | Horseshoe Lake | Cass | MN | A | 12 ft | 127 acres | 0 |
| 2 | Shallow Lake | Hubbard | MN | A | 10 ft | 284 acres | 13 |
| 3 | Norway Lake | Cass | MN | A | 12 ft | 515 acres | 14 |
| 4 | Crooked Lake | Lake | MN | A | 4 ft | 60 acres | 0 |
| 5 | Spider Lake | Chisago | MN | A | 9 ft | 131 acres | 7 |
| 6 | Mill Lake | Becker | MN | A | 10 ft | 155 acres | 14 |
Frequently Asked Questions
Are shallow lakes safe for swimming?
Many shallow lakes are safe for swimming, especially those with Grade A or B water quality. However, shallow lakes are more prone to algae blooms in late summer due to warmer water temperatures and wind-mixed nutrients. Always check for blue-green algae advisories before swimming.
Why do shallow lakes have more algae?
Shallow lakes warm up faster and wind mixes nutrients from the bottom into the water column, fueling algae growth. Without a thermocline to trap nutrients in deep water, the entire lake becomes a growth zone for algae. This is why shallow lakes are more likely to receive lower water quality grades.
Source: EPA National Aquatic Resource Surveys, 2026.