The Wendwater is a river located in the southeastern Crownlands and northeastern Stormlands. Beginning at a narrow lake in the southern Kingswood, it flows northeast to Blackwater Bay. North and west of the Wendwater is the forest of the Kingswood, while to the east is Massey's Hook. It is possible the river's name is related to House Wendwater.
A Clash of Kings
En route to King's Landing, Stannis Baratheon's fleet anchors at the mouth of the Wendwater. Ser Imry Florent, Lord High Captain of Stannis's fleet, calls for a meeting of captains to instruct them in the battle plan once they reach the Blackwater Rush. Three days later they attack King's Landing in the Battle of the Blackwater.