Tankumsee, Artificial lake in Isenbüttel, Germany.

Tankumsee is an artificial lake in Isenbüttel, about 800 m by 1300 m and up to 16.7 m deep, created as a gravel pit during construction of the Elbe-Seitenkanal. Its shore has a sand beach over 1000 m long with a shallow "Babybucht" watched over by a wooden DLRG lifeguard tower. Around the 57-hectare water lie holiday homes, boat rental and sports facilities.

Sand dredged for the dam of the Elbe Side Canal left the hollow that became Tankumsee in the early 1970s. In 1972 municipal bodies founded the Tankumsee planning and development company, which bought and opened up the land. The lake was officially commissioned on 26 June 1976. A holiday-home colony of around 200 houses later turned into a permanent residential area.

The name Tankum is an old field name for the farmland that lay here before the lake was dug. It is thought to come from the pre-Germanic root Tank/Tang, meaning algal mass and later bog or bog water; the ending -um may echo an extinct word for swamp, fitting the marshy Barnbruch. The DLRG lifeguard tower at the shallow "Babybucht" is a landmark of the bathing operation.

The lake sits within a large recreation area and is easy to reach with ample parking for visitors. Swimming conditions are best during warmer months when water temperature is comfortable and all facilities are fully operational.

On the far shore stands a wooden DLRG lifeguard tower, its square cabin raised on four legs and marked with the letters "DLRG" above the open viewing slats. It watches over the "Babybucht", a shallow-water cove where small children play under supervision. The German Life-Saving Society (DLRG) is responsible for guarding bathers here.