Semerwater is the largest natural lake in North Yorkshire, England. It is half a mile (800 m) long, covers 100 acres (0.40 km2) and lies in Raydale, opposite England's shortest river The River Bain. A private pay and display parking area is at the foot of the lake. Semerwater attracts canoers, windsurfers, yachtsmen and fishermen. There are three small settlements nearby:
Semerwater is the setting for a well-known legend within Yorkshire. According to the tale, long ago the spot was occupied by a prosperous city. One night an old man (or in some versions, an angel in disguise) came down to the city, in search of food and drink. He went from door to door, and at each house he was turned away. Finally, he came to the hovel of a poor couple just outside the town; the couple took him in and treated him with great kindness.