The megamouth shark (Megachasma pelagios) is one of the rarest and most elusive sharks on Earth. Discovered only in 1976 when a U.S. Navy ship accidentally snagged one off Hawaii, it was at first mistaken for a sea monster. With its oversized, rubbery mouth and flabby, slow-moving body, it looks unlike any other shark. Scientists now know it is a deep-sea filter feeder, swimming slowly through the dark with its huge mouth open to scoop up plankton and jellyfish.
Because sightings are so rare, the megamouth remains one of the ocean’s biggest mysteries.
Megamouth Sharks At-A-Glance
Scientific Name: Megachasma pelagios
How big do megamouth sharks get? Up to 17 feet (5 meters), though most are around 13 feet (4 meters). The very first specimen measured nearly 15 feet and weighed about 1,650 pounds.
Do megamouth sharks have teeth? Yes! But not like you imagine. About 50 rows in the upper jaw and 75 in the lower, though most are tiny and nonfunctional.
Where do they live? Megamouth sharks are found in Deep tropical and subtropical waters worldwide, especially the Pacific and Indian Oceans. Seen off Japan, Taiwan, the Philippines, and Hawaii.
What depth are the megamouth sharks found at? Typically 1,640–3,280 feet / 500–1,000 meters during the day, rising toward the surface at night to feed.
What do megamouth sharks eat? Plankton, jellyfish, and other tiny organisms filtered from the water.
How do megamouth’s give birth? Ovoviviparous — embryos develop in eggs inside the mother, hatch internally, and are born live. Check out our megamouth research page for recent findings!
How long do they live? Unknown, but may be 30 years or more.
What is the IUCN conservation status? The megamouth shark is listed as least concern, but let’s clarify. Very little is understood about their populations.
Frequently Asked Questions about Megamouths
Are megamouth sharks dangerous?
No. They are filter feeders and pose no threat to humans.
Why are they called megamouth sharks?
Because of their massive, wide mouths, which they use to scoop up plankton.
Where do megamouth sharks live?
In deep water in tropical and subtropical regions, often spending days in the dark depths and nights closer to the surface.
How rare are megamouth sharks?
Extremely rare. Only around 100 individuals have been officially recorded worldwide.
Bet you didn’t know this about megamouth sharks….
- The megamouth gets its name from its enormous, rubbery mouth, which can stretch over a meter wide.
- Tissue inside its lips may be bioluminescent or light-reflective, possibly attracting plankton into its mouth.
- Unlike sleek, muscular sharks, megamouths have soft, weak muscles and swim so slowly that scientists once described one as “a big sock puppet with fins.”
- This shark is in its own family, but it shares filter-feeding habits with basking and whale sharks.
- Fewer than 100 confirmed specimens have ever been seen or caught worldwide, making it one of the rarest sharks we know.
Ready to Dive In with Megamouth Sharks?
Direct sightings of megamouth sharks are extraordinary, but a few notable places where they’ve been observed include:
- Off the coast of Japan (Okinawa and Shizuoka Prefecture)
- Taiwan’s east coast, particularly between April and August
- Hawaii, where the very first specimen was discovered in 1976
Because they live so deep and are rarely encountered, they are not a common target for divers. But every sighting is a major event for shark researchers, offering one more clue to understanding this mysterious giant.
Science in the Spotlight: Megmouth Research
Even though so few megamouths have been studied, scientists have made exciting discoveries in just the past few years.
- In 2024, tagging studies in the northwest Pacific confirmed that megamouths migrate vertically — staying deep during the day and rising at night to feed on plankton.
- In 2023, a female that washed ashore in the Philippines was found pregnant with seven pups, proving for the first time that megamouths give live birth.
- Also in 2023, two megamouths were seen together off California — the first evidence of possible social or mating behavior.
- In 2025, new records were reported from India and the Southwest Atlantic, expanding their known global range to over 273 specimens.
What we still don’t know: how long they live, how fast they grow, their full migration routes, and how often they reproduce.
After Bites Megamouth Quiz
Take the megamouth trivia quiz and test your new found knowledge.