The megamouth shark has a sturdy body, and a fat, round and long head. The snout is very short and wide. The gill slits are quite long but can not reach the dorsal surface of the head. The mouth is wide, with the corners extending behind the eyes. The first dorsal fin is located more closely to the pectoral fins than to the pelvic fin, and the second dorsal fin is less than half the size of the first dorsal fin. Both dorsal fins are low. The pectoral fins of the adults are shorter than the head in length. 