[3] The first megamouth shark was captured on November 15, 1976, about 25 miles northeast of Kahuku, Hawaii, when it became entangled in the sea anchor of United States Navy ship AFB-14 at a depth of about 165 m (541 ft).

[5] Examination of the 4.5-meter (15 ft), 750-kilogram (1,650 lb) specimen by Leighton Taylor showed it to be an entirely unknown type of shark, making it – along with the coelacanth – one of the more sensational discoveries in 20th-century ichthyology.

Japan, the Philippines and Taiwan have each yielded at least 10 specimens, the most of any single area, amounting to more than half the worldwide total.

Specimens have also been sighted in or come out of the waters near Hawaii, California, Mexico, Indonesia, Australia, Brazil, Senegal, South Africa, Puerto Rico, Ecuador,[7] and possibly Vietnam.

[8] In addition to the living M. pelagios, however, two extinct megamouth species – the Priabonian M. alisonae[9] and the Oligocene–Miocene M. applegatei – have also recently been proposed on the basis of fossilized tooth remains.

It has a brownish-black colour on top, is white underneath, and has an asymmetrical tail with a long upper lobe, similar to that of the thresher shark.

This lip was initially thought to be possibly embedded by luminous photophores when the first shark was examined in the early 1980s, which may act as a lure for plankton, while the team examining the second shark in the mid-1980s instead proposed that the lower lip might glow with the white band used as a reflector of sorts, but neither theory has been proven.

[21] This white band is present in both sexes and could be either a feeding mechanism or possibly be used as a means of identifying other individuals of megamouth sharks.

[citation needed] Reproduction is ovoviviparous, meaning that the young sharks develop in eggs that remain within the mother's body until they hatch.