Manatees and their close relatives, sea cows and dugongs, may have been the inspiration for the mermaid legend. The scientific family name for sea cows is Sirenus, which is derived from the word “siren”—the original name for the beautiful mermaids that lured love-struck sailors to their deaths in ancient legends.

The orca or killer whale (Orcinus orca) is the fastest swimming whale. In fact, it is the fastest swimming marine mammal with speeds that reach 31 miles per hour (50 kilometers per hour).