The lake appears to have the shape of a Psyduck's flipper. It is also surrounded by many kinds of Berries.
Several Psyduck retreated from the lake after three Muk took over, forcing them to block a road so that three Psyduck Eggs could hatch.
Ash and his friends helped in driving the Muk away so that the Psyduck and their new Psyducklings could go back to the lake and stop blocking the road. The Muk went to another nearby lake, which is very polluted.