So it's perhaps not strange that sharks are unique among fish in many ways.

University of Hawai'i graduate student Yannis Papastamatiou, who studies sharks with university shark expert Kim Holland, said sharks hardly deserve the reputation they have as ferocious, constantly hunting eating machines.

"Sharks have been feared for many years, wrongly," he said. Most of them eat seldom, eat fairly small portions, and mammals tend to be a negligible part of most sharks' diets.

But they're still top predators and all carnivores, although many get their meat in the form of tiny shrimps.

Whale sharks — the biggest fish in the sea at 40 or more feet long — don't bite. They are filter feeders swimming with their mouths open, ingesting zooplankton — tiny animals that swim in the water column.

There are many species of small sharks, like the cookie-cutter shark, which grows to about 18 inches long. They swim up to seals, tuna and other marine life, and rip out chunks the size of half a golf ball or, as their name suggests, a cookie.

"The majority of sharks are less than three feet long," said zoologist Jerry Crowe, curator at Waikiki Aquarium.

If you happen to be eating shark meat, you're unlikely to choke on a bone. They don't have any. Instead, their skeletal structures are made of cartilage.

Most fish can't close their eyes, but many sharks can, using a specialized eyelid.

When a shark bites, marine biologists try to find a tooth or the imprint of a tooth, since tooth shape is a key in identifying shark species. Sharks can lose teeth without causing themselves problems. They have rows of new teeth lined up behind the ones currently in use.

Shark skin is extraordinarily tough, largely because of a coating of bony tooth-like structures. It's so hardy that people have used sharkskin as sandpaper.

Sharks, for the most part, have very good eyesight, contrary to conventional wisdom. And the ability of some species to see in low light is far superior to that of humans.

Some — like great whites, hammerheads, Galapagos and tigers — are gray, leading some folks to refer to a shark as "the man in the gray suit." The stripes that give tigers their name are obvious in young animals but fade with age.

But many sharks aren't gray and have colorful skin patterns. Sand tigers are golden colored with spots. Threshers, makos and blues have blue colorations. Basking sharks can be mottled gray-brown to black. Blacktip and whitetips have distinct coloration, as their names suggest, on the tips of their fins. A whale shark has spots and stripes.

A zebra shark doesn't have stripes, as its name might suggest, but dark leopard-like spots on a yellow to green-brown background. The leopard shark has some spots, but its most distinctive features are elongated markings like saddles across its back.

Sharks are important figures in Hawaiian culture. Some families revere sharks as personal protectors. And some Hawaiian warriors had a kind of graduation ceremony that involved killing a man-eating shark. Cutting tools and weapons were made using sharks' teeth.

Still, the shark's reputation as a fearsome predator is what attracts most of the attention, and in a way, that's what Papastamatiou finds interesting.

"A number of the species (of sharks) are obviously top-level predators in the ocean, which gives them an ecological significance. What happens if you remove one from the ocean — what happens to their prey, and the prey's prey?

"We know very little about these impacts," Papastamatiou said.