Historical evidence for mermaids?

This article describes an old museum exhibit that took the viewer through a series of mythical creatures and the historical basis for them. But one thing I never knew-Christopher Columbus wrote in his journal that he saw a mermaid, but that it was "not as pretty as they are depicted, for somehow in the face they look like men." Modern scientists claim what he really saw was a manatee, and at the exhibit they would superimpose a picture of a manatee over a mermaid to explain the confusion. But...really? Here's John William Waterhouse's mermaid:

Here's a manatee. I don't see any resemblance at all. Maybe Columbus needed glasses.

The article goes on to say that John Smith also saw a mermaid, but unlike Columbus, he thought she was "by no means unattractive."

Urban legends describes how the supposed washed-up skeleton of a mermaid that was sent around by email is a hoax. Taxidermists would combine bodies of monkeys with fish. Mermaid.net has interesting reading on the evolutionary possibilities of mermaids existing, though admits that there is no proof.

Supposed "real mermaid"