Megachasma pelagios, commonly known as the megamouth shark, is a rare deep-water species known for its enormous mouth and unique filter-feeding behavior. Typically found in deep ocean waters, it is characterized by its flabby body, bioluminescent mouth lining, and slow, deliberate swimming style.

Megachasma pelagios, commonly known as the megamouth shark, is primarily found in the Pacific, Atlantic, and Indian Oceans. Its distribution is quite broad and includes regions such as the waters off the coast of Japan, Taiwan, the Philippines, Hawaii, California, and the deep waters of the Indian Ocean. The exact range is still being studied due to the species' elusive nature.

The megamouth shark inhabits deep oceanic waters, typically found at depths ranging from 150 to 1000 meters, although it can occasionally be found near the surface. It is adapted to a pelagic lifestyle in temperate to tropical marine environments.

The megamouth shark occupies a unique niche as a filter feeder in the deep ocean. It primarily feeds on planktonic organisms, such as krill and small jellyfish, using its large mouth to filter food from the water. Its ecological role involves maintaining the balance of plankton populations in the deep sea ecosystems.