Groenvlei is the only lake in Wilderness which is not part of the Wilderness National Park, but this is no reflection on the lake's beauty. Situated just outside of Sedgefield in the Western Cape, Groenvlei is the only lake that is purely fresh water and without an inlet or an outlet. The lake is maintained by rainwater and springs alone.
Known as one of the few lakes in South Africa that contains naturally occurring largemouth bass, Groenvlei has strict restrictions on boating. Only electric motors are allowed on the lake and outboard motors have to be lifted clear of the water. The water depth is rather shallow, at only 3m in some places and with plenty of water grass and reeds. The Garden Route Bass Classic is held at Groenvlei in late April each year.