(Photo: Ravaux J, Hamel G, Zbinden M, Tasiemski AA, Boutet I, PLoS ONE)
It may look more like an animal than the others on this list, but it's more surprising the Pompeii worm is actually alive, given the high temperatures it endures living attached to hydrothermal vents. It survives blasts of water as hot as 176 degrees Fahrenheit, despite the scientific consensus that animals can't tolerate temperatures above 122 degrees. How it manages remains a mystery, but scientists think the hair-like bacteria on the Pompeii worm could act as insulation against the heat.
7. Sea Butterflies
(Photo: Flickr, Kevin Raskoff, NOAA)