It's true! Cartoonist Zach Weinersmith points out that some species of turtle can breathe through their cloacas. They can absorb oxygen in air through their lungs and oxygen in water through their cloacas. Physiologist Donald C. Jackson explains:
Whether the turtle breathes air or water depends on which avenue is open. For lung ventilation, the turtle, with its head out of the water, opens its glottis and air passes in and out its lungs; for cloacal irrigation while submerged, the turtle opens its anal spincter and water passes in and out of its cloaca.
We humans can't do this. Sometimes I think we drew the short straw in evolution.
P.S. Superhero idea: a teenager is bitten by a radioactive turtle. He develops this ability, among other turtle-based superpowers.