Cetaceans (from the Latin word cetus, coming from the Ancient Greek κῆτος (kêtos) 'huge fish or sea monster') are an infraorder of aquatic mammals belonging to the order Artiodactyla that includes whales, dolphins, and porpoises. Key characteristics of its species is the full adaptation to an aquatic life cycle, a streamlined body shape, often a large size and exclusively a carnivorous diet. They propel themselves through the water with powerful up-and-down movement of their tail which ends in a paddle-like fluke, using their flipper-shaped forelimbs to maneuver.
Cetaceans are grouped into two taxonomic suborders: the baleen whales (Mysticeti) and the toothed whales (Odontoceti). Mysticetes are filter feeders that forage for zooplankton and small fish by skimming or gulping huge amounts of prey and water. The water is then forced back out the mouth past hundreds of baleen plates that act as sieves to trap the prey, which is then swallowed. Odontocetes have various numbers of identical conical or spade-shaped teeth that are used to strain or grasp prey, primarily fish and squid. Odontoceti are generally capable of echolocation. They can discern the size, shape, surface characteristics, distance and movement of an object. They can search for, chase and catch fast-swimming prey in total darkness.