The crocodile shark ("Pseudocarcharias kamoharai") is a species of mackerel shark and the only extant member of the family Pseudocarchariidae. A specialized inhabitant of the mesopelagic zone, the crocodile shark can be found worldwide in tropical waters from the surface to a depth of . It performs a diel vertical migration, staying below a depth of during the day and ascending into shallower water at night to feed. Typically measuring only in length, the crocodile shark is the smallest living mackerel shark. It can be distinguished by its elongated cigar-shaped body, extremely large eyes, and relatively small fins.