The raft spider, Dolomedes fimbriatus, is a European spider of the family Pisauridae. The raft spider is one of the two largest spiders in the United Kingdom. Like other Dolomedes spiders it hunts by running on the surface of water, and can submerge altogether to hide from predators. The female's body measures up to 22 millimetres (0.87 in) long with a leg span of about 70 mm (2.8 in); as with most spiders the male is considerably smaller.