A submerged male fen raft spider (Dolomedes plantarius), a semi-aquatic fishing (or raft) spider. Fishing spiders can swim on or under water, and hide there or hunt for prey. While submerged, the spider is covered with a thin layer of air, keeping it dry. Part of the family Pisauridae, nursery web spiders. This is one of the largest spiders in northern Europe, but it is becoming less frequent, nearly extinct in many countries and is considered vulnerable in the 2009 IUCN red list.