Lau

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http://beastpedia.blogspot.com/2014/02/post-revamp-lau.html

The Lau is, supposedly, a 30-foot long freshwater snake or fish that lives in certain African lakes. Since these creatures are virtually never sighted, they most likely spend their lives entirely or mostly underwater. Thus, a long fish like a catfish or ropefish of a new, giant species is the most likely explanation for this beast. The Lau is said to have tentacles on its face, which could represent the whiskers or facial tentacles of a catfish or ropefish. few snakes have this feature so it is most likely not a reptile. Few reptiles could thrive in the depths of a lake anyway. The "snake" aspect of this cryptid is likely an exaggeration, as is its length-- though maybe not by much.

Image from http://img.poptower.com/pic-9106/jeremy-wade.jpg?d=600