Evolution of cetaceans "Caperea marginata") all have derived characteristics presently unknown in any cetothere and vice versa (such as a sagittal crest). The adaptation of echolocation occurred when toothed whales (Odontoceti) split apart from baleen whales, and distinguishes modern toothed whales from fully aquatic archaeocetes. This happened around 34 million years ago in a second cetacean radiation. Modern toothed whales do not rely on their sense of sight, but rather on their sonar to hunt prey. Echolocation also allowed toothed whales to dive deeper in search of food, with light no longer necessary for navigation, which opened up new food sources. Toothed whales
Captive killer whales water, and holding under water. Killer whales biting trainers during feeding or shows is generally the mildest form of attack seen, but can escalate to an animal dragging the trainer underwater and holding them there until they lose consciousness or drown. Trainers who have had killer whales ram into them in the water tend to suffer from a range of injuries including internal bleeding, broken bones, ruptured organs, and heart attack. Tilikum, a large bull male killer whale who died in early 2017, had been involved in the death of three individuals since his capture near Iceland in November 1983.