Water Opossum (Chironectes minimus)
Also known as the yapok, the water opossum is a species of semi-aquatic marsupial found in Mexico and parts of Central and South America. Like most opossums this species does have a pouch, but the pouch is found in both sexes a trait only found in the extinct thylacine. As its name suggests this opossum is mainly aquatic, living near riverbanks and swimming at night to catch fish and crustaceans. They are the only known extant marsupial to live this lifestyle. Living near water presents problems for a marsupial as they keep their young in a pouch, however the water opossum has a evolved a way to combat this it has a strong ring of muscle which can close the pouch and make it watertight, so the young don’t drown when the mother is swimming.