Greater white

A greater white, shown with a human in the lower left corner for scale. Note that perspective and pose hides the greater white's actual length.

The mercifully rare greater white (Leviathan dominatus) is Poseidon's unquestioned apex predator, and only the carrying capacity of Poseidon's ecosystem makes marine travel acceptably safe. Weighing as much as Earth's extinct blue whales and measuring up to three times longer, each greater white supports an ecology of parasites, sessile organisms, algae, and cleaner species that feed off them. To protect themselves, greater whites have a constantly-shedding skin that peels off in rotting sheets, giving them their distinctive off-white coloration and stench.

Much like Earth's baleen whales, greater whites are essentially filter feeders, subsisting primarily on copeoids, big round things, sargassum mats, entire shoals of fish, and other things they can swallow whole. Unlike Earth's baleen whales, greater whites supplement this diet with almost anything else they encounter, up to and including marine vehicles.

Able to track prey by acoustics, waterborne vibration, or electromagnetic activity, greater whites will attack underwater with bites and ramming. Their most dangerous attack, reserved for surface attacks, is to breach and land on top of their target, usually reducing it to a debris field. After breaching, greater whites typically swim back through the debris, swallowing everything in it.