Grass Lake in Codington County, South Dakota, is a substantial waterbody located in the Glacial Lakes region of northeastern South Dakota. With approximately 500 acres of water surface and several miles of shoreline, this lake offers paddlers a scenic experience characteristic of prairie pothole wetlands. The lake features a rocky and sandy bottom in some areas, transitioning to mudflats in others, creating diverse shoreline conditions.

Access is available from multiple points around the lake, with the primary access located off county roads on the western side. The western shoreline can be particularly challenging to navigate by vehicle, with rough roads that may be impassable during wet conditions, though these areas are suitable for hiking access.

The lake's ecology is notable for its heron and egret colonies, particularly in cottonwood trees along the eastern shore. Paddlers can expect to observe Great Egrets, Snowy Egrets, Black-crowned Night-Herons, and Cattle Egrets, especially during breeding season. The area also supports diverse waterfowl including Redheads, Ruddy Ducks, and various diving and dabbling duck species. Black Terns and Forster's Terns are common, along with American White Pelicans, Wilson's Phalaropes, and other marsh birds. The nationally endangered Piping Plover has been recorded nesting in small numbers along the shoreline.

The lake's water quality is generally good, supporting populations of walleye, northern pike, and other game fish. Vegetation around the shoreline includes native grasses and wetland plants, providing excellent wildlife viewing opportunities. White-faced Ibis have also been documented in the area.

A $5 vehicle day-use fee applies at developed access points. Paddlers should be prepared for prairie winds that can create choppy conditions on this exposed lake. The lake is managed by South Dakota Game, Fish and Parks and is recognized as an Important Bird Area, making it particularly valuable for birding-oriented paddlers.