Cetacea and two (external) limbs that are modified into flippers. Though not as flexible or agile as seals, cetaceans can swim very quickly, with the killer whale able to travel at in short bursts and the fin whale able to cruise at . Dolphins are able to make very tight turns while swimming at high speeds. The hindlimbs of cetaceans are internal, and are thought to be vestigial. Baleen whales have short hairs on their mouth, unlike the toothed whales. Cetaceans have well-developed senses—their eyesight and hearing are adapted for both air and water, and baleen whales have a tactile system
Captive killer whales twice that length or and a minimum depth of , giving a minimum volume of for two killer whales. Each additional killer whale requires a pool with an additional of volume. 9 CFR 3.104 also requires a minimum of surface area per killer whale in Table IV (the example with a cylindrical tank in diameter for two whales provides of surface area per killer whale). Swiss regulations require a larger minimum volume: × deep for two killer whales, or . The Alliance of Marine Mammal Parks and Aquariums (AMMPA) goes further, and recommends for two killer whales. The US exhibitors