A rare Megamouth shark which was caught 800 meters under the sea was cut open in the city of Shizuoka, Japan in front of more than 1,500 viewers.

Japanese spectators watched as the four-meter 'alien shark' was subjected to a public autopsy and cut open outside the Marine Science Museum in Shizuoka, according to Daily Mail.

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The underwater monster is believed to be able to grow to a length of up to five meters. The Megamouth shark spends majority of its time swimming at deep levels of the ocean and only goes to the surface at night for its meal.

Based on a website containing the shark's biology, the Megamouth feeds mostly on the shrimp-like krill. It also preys on euphausiid shrimps, the Pancake Jellyfish, copepods, and other planktonic animals.

The deep-sea creature devours small fishes by filtering them using the inner layer of its gills.

This is the 13^th time that such a monster has been caught in Japan. This is also that 58^th time that it has been seen in the country.

The Museum of Western Australia said the first Megamouth shark was caught 165 meters down the Hawaiian waters when an anchor of a big research ship snagged its teeth.

The museum also has its own specimen of the said shark, which they found washed up on Western Australian shore in August 1988.

Several more sharks have also been sighted ashore either dying or already dead. Of the 58 specimens sighted, a fourth of these creatures have been caught by fishermen to be eaten.

The Discovery Channel coined the term 'alien shark' during a recent tribute it made for the Megashark. The channel featured the said shark in one of its Shark Week episodes.