Afraid to go into the ocean after the first time you watched Jaws? This could have a similar effect, although it's largely an urban phenomenon. National Geographic shows just how easy it is for sewer rats to swim up through a toilet bowl. Their ribs are hinged at the spine, which makes it easy for them to travel through pipes and plumbing. Rats are also expert swimmers, they can hold their breath underwater for up to three minutes and can tread water for three days in a row.
via Laughing Squid