It is a deepwater sharks, the smallest of the three filter feeders. Only 53 (1 unconfirmed) of these animals have been caught/sighted since May 2014, with three being recorded on film. In fact, one was this year! When seen, this animal is easily recognizable due to its large lips, large head and small eyes. It is brownish/black on top, white underneath, and has a tail with a long upper lobe (seen in the thresher shark).
Like the other filter feeders, it swims slowly with its mouth wide open, filtering water for small prey like krill, plankton, jellyfish, small fish, fish eggs, etc. Their teeth are small, like the other filter feeders, not getting much use. However there is ONE very cool thing about the megamouth mouth.
The mouth has a luminous upper jaw member, thanks to photophores, which may act as a lure for their prey. Glow-in-the-dark mouth? Yes, please!
In 1990, a 4.9-m (16 ft) male specimen was caught near water's surface in California. This guy was swam off with a small radio tag attached. The tag captured depth/time data for two days. During the day, the shark swam around 120–160 m (400–525 ft) deep, but as the sun set, it would swim to the surface and spend the night between 12 and 25 m (39–80 ft). Both day and night, it swam slowly, about 1.5–2.1 km/h (1–1.3 mph). This daily migration is seen in many marine animals as they move with plankton in the water column. Megamouth are specially adapted for this by having a poorly calcified cartilaginous skeleton and soft, squishy body.
Reproduction is ovoviviparous, although litter sizes are unknown. However, in table some of the specimens were sexually mature and recently had engaged in mating. Claspers of one specimen were oozing with spermatophores.
The only confirmed register of a megamouth predator is an isolated event of sperm whales (Physeter macrocephalus) attacking this shark. This occurred in Manado, North Sulawesi, Indonesia (30th August 1998) near midday, while some researchers were observing the whales. The base of the dorsal fin and the gills of the shark showed signs of the whales' attack.
I mean, have you seen the size of the tiny shark compared to this giant animal? Definitely falls into the category of "parasite" rather than "predator."
A few species of parasites have been observed in megamouth sharks, including specimens of a cestode worm species (Corrugatocephalum ouei) and some poorly studied trypanorhynch (Mixodigma leptaleum) recovered from the intestine of one of the discovered megamouth. A microscopic parasite (Chloromyxum) was also found in a megamouth's gall bladder.
Due to the lack of information concerning distribution and population status, the megamouth is considered "Data Deficient" by the World Conservation Union (IUCN).
Here's a great video last year's Alien Sharks: The Megamouth captured, which aired during Shark Week 2013: