A specialized inhabitant of the mesopelagic zone, the crocodile shark can be found worldwide in tropical waters from the surface to a depth of 590 m (1,940 ft).

It performs a diel vertical migration, staying below a depth of 200 m (660 ft) during the day and ascending into shallower water at night to feed.

An active-swimming predator of pelagic bony fishes, squid and shrimp, the crocodile shark has a sizable oily liver that allows it to maintain its position in the water column with minimal effort.

[3] The crocodile shark was first described as Carcharias kamoharai in a 1936 issue of Zoological Magazine (Tokyo) by ichthyologist Kiyomatsu Matsubara, based on a 73.5 cm (28.9 in) long specimen found at the Koti Fish Market in Japan.

[5] Fossil Pseudocarcharias teeth dating to the Serravallian age (13.6–11.6 Ma) of the Miocene epoch have been found in Italy, and are identical to those of the modern-day crocodile shark.

The sizable, arched jaws can be protruded almost to the tip of the snout and contain large teeth, shaped like spikes in the front and knives on the sides.

In the Pacific, it occurs from Japan, Taiwan, and the Korean Peninsula in the northwest, southward to Indonesia, Australia, and New Zealand, and eastward to the western coast of the Americas from Baja California to Chile, including the Marshall, Phoenix, Palmyra, Johnston, Marquesas, Line, and Hawaiian Islands in between.

It is occasionally encountered inshore near the bottom and has been known to strand on the beaches of South Africa, possibly after being stunned by upwellings of cold water.

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.

[5][7] 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.

[12] The large eyes of the crocodile shark, equipped with a reflective green or yellow retina and lacking an expanded iris, suggest that it is a nocturnal hunter that relies on sight to pick out the silhouettes or bioluminescence of its prey.

[7] Little is known of the crocodile shark's feeding habits; it is thought to be an active, fast-swimming predator based on its strong musculature, large tail, and behavior when captured.

On one occasion, a crocodile shark off Cape Point, South Africa, jumped out of the water in pursuit of bait.

Coupled with its low reproductive rate, this has led the International Union for Conservation of Nature (IUCN) to assessed it as Near Threatened.

[16] After AT&T installed the first deep sea fiberoptic cables between Gran Canaria and Tenerife in the Canary Islands in September 1985, the system suffered a series of shorts that necessitated costly repairs.