Brain Eating Amoebas: They're Horrifying and They Look Like Clowns

Here's another reason never to go swimming:

This rare form of parasitic meningitis—primary amebic meningoencephalitis (PAM)—is caused by an amoeba called Naegleria fowleri. That microscopic amoeba—part of the class of life called protozoans—is a naturally occurring organism that normally feeds on bacteria and tends to live in the sedimentary layer of warm lakes and ponds.