A marine science instructor snorkeling off the Southern California coast spotted something out of a fantasy novel: the silvery carcass of an 18-foot-long (5-meter-long), serpent-like oarfish.

Jasmine Santana of the Catalina Island Marine Institute needed more than 15 helpers to drag the giant sea creature to shore on Sunday.

Staffers at the institute are calling it the discovery of a lifetime.

"We've never seen a fish this big," said Mark Waddington, senior captain of the Tole Mour, CIMI's sail training ship. "The last oarfish we saw was three feet long."

Because oarfish dive more than 3,000 feet (914 meters) deep, sightings of the creatures are rare and they are largely unstudied, according to CIMI.

The obscure fish apparently died of natural causes. Tissue samples and video footage were sent to be studied by biologists at the University of California, Santa Barbara.

Santana spotted something shimmering about 30 feet (9 meters) deep while snorkeling during a staff trip in Toyon Bay at Santa Catalina Island.

"She said, `I have to drag this thing out of here or nobody will believe me,'" Waddington said.

After she dragged the carcass by the tail for more than 75 feet (23 meters), staffers waded in and helped her bring it to shore.

The carcass was on display Tuesday for students studying at CIMI. It will be buried in the sand until it decomposes and then its skeleton will be reconstituted for display, Waddington said.

The oarfish, which can grow to more than 50 feet (15 meters), is a deep-water pelagic fish _ the longest bony fish in the world, according to CIMI.

They are likely responsible for sea serpent legends throughout history.