Candiru

If you watched Grey's Anatomy last night you've probably seen the penis fish. You're also probably a girl. What they left out of the explanation, is that the Vandellia cirrhosa is in fact just as happy to swim up a vagina, or in fact any opening/orifice. It is a type of parasitic catfish that usually lodges itself in the gills of other fish and feeds on their blood. There is no reported case in pubmed, other than it is a gift to urology (?), but natives living on the amazon fear it (understandably so). However, reports of the fish swimming in the urine stream into the penis outside of the water are an urban legend. But if you are submerged , then beware. I'm scared of channel catfish myself...