Deep-sea gigantism

Deep-sea gigantism is the phenomenon where animals living in the ocean's deepest, darkest regions grow to enormous sizes compared to their shallow-water relatives. Scientists believe this happens because the deep sea has fewer predators and competitors, allowing giant squid, isopods, and other creatures to evolve larger bodies without the same survival disadvantages they'd face in crowded surface waters. The cold temperatures and high pressure of the deep ocean may also slow metabolism, making it easier for these animals to sustain their massive frames on the limited food that drifts down from above.