With a long body, small fins, and large liver rich in squalene and other low-density lipids, the crocodile shark is convergently similar to mesopelagic dogfish sharks such as the cookiecutter shark ("Isistius brasiliensis"). The liver may comprise a fifth of the shark's weight, and acts as an incompressible float that allows it to maintain neutral buoyancy in the water column with little effort. Like many other inhabitants of the mesopelagic zone, the crocodile shark apparently migrates closer to the surface at night to feed and descends into deeper water during the day, being rarely found above a depth of 200 m (660 ft) during daytime.