Megamouth sharks troll the deep sea for the smallest bits of food, plankton and krill, trapping them in the massive caves that are their jaws. They are mysterious and extraordinarily rare -- and almost never seen by humans.

But on Wednesday, a 15-foot adult male megamouth washed up on the shores of Barangay Marigondon in the Philippines. The shark was dead, but its discovery was still thrilling. There is confirmed evidence of just 64 sightings of the shark, not counting a few more fishermen's tales that have not been verified with documentation or images.

"We know so little about it," Christopher Bird, a PhD candidate who studies deep-sea sharks at University of Southampton, said of the megamouth species. "It wasn't discovered really until 1976. It's only really seen when it's accidentally caught in fishermen's nets or when it is stranded on beaches."

The megamouth, Bird told The Washington Post, is one of his favorite shark species. "It's just the mystery behind it," he said.

Most of the previous sightings have occurred in the Pacific Ocean near Taiwan, Japan or the Philippines -- though the sharks have been occasionally caught elsewhere. But they have been so rarely spotted that it is unknown exactly how big the world's population might be, and where most of them reside, according to researchers.

When they do appear -- which usually occurs when they swim closer to the surface to follow their food, it offers a rare opportunity to examine the little-known creature.

This particular shark is being preserved on ice until an necropsy can be performed, and a cause of death can be determined. Albay Parks and Wildlife Center in the Philippines is likely to put the shark's body on display.

Nicknamed "toothless" by locals, the shark is anything but that. Megamouths have an abundance of teeth lined in as many as 50 rows in their enormous jaws. A few of those rows act as a filter to keep food in and push water out. A white band on a megamouth's upper lip might also serve as a bio-luminescent strip that helps it attract food in the dark water, though researchers aren't certain of that.

Megamouth sharks are relatively docile deep-sea dwellers that sometimes find themselves prey to whales or other sharks. Though they aren't the best swimmers, they do pretty well for themselves sucking tiny bits of food into their mouths as they cruise around in the ocean.

You might be wondering, "what does it taste like?" The answer, according to researchers, is pretty good, at least when battered and fried. But eating the large shark is generally frowned upon, mostly because of how rare they are, and also because they are believed to store toxins.