Its total watershed (the combined drainage areas of the Fox and Wolf Rivers plus minor tributaries) is 5,566.2 square miles (14,416 km2).

The lake is polymictic, maintaining a continuously mixed water column with no patterns of seasonal temperature stratification.

[5] Large algal blooms and high E. coli populations occasionally make the water unsafe for swimming.

Invasive species include Chinese mystery snail, curly-leaf pondweed, Eurasian watermilfoil, round goby, rusty crayfish, and zebra mussel.

The unincorporated community of Butte des Morts lies on the lake's northern shore, west of Oshkosh.

[10] Terrell's Island is a DNR-organized wetlands conservation project located on the south shore, enclosed by a breakwall that extends some distance into the lake.