A Catalina Island Marine Science instructor ran into a giant "sea serpent" while enjoying a Sunday dive.

Marine science instructor Jasmine Santana spotted the 18-foot-long oarfish off about 22 miles off the port of Los Angeles, KTLA 5 reported.

Santana said the find was the "discovery of a lifetime."

The fish was dead, but mostly intact. The researchers believe the eel-like fish died of natural causes.

"It took 15 or 20 of us to pick it up," Jeff Chace, a program director with CIMI, said.

The creature had "eyes the size of silver dollars," according to the diver who discovered the sea monster, Press-Telegram reported.

Oarfish are mysterious because they can dive to depths of 3,000 feet, they are considered to be the longest species of bony fish.

CIMI instructors were unloading gear when they saw Santana dragging the behemoth to shore, KTLA reported.

"The craziest thing we saw during our two day-journey at sea happened when we got home. These islands never cease to amaze," instructor Connor Gallagher said, according to a news release, KTLA reported.

The researchers are trying to decide what they should do with the oarfish's body.

"We can't even really fit it into our freezer," Chace said.

Officials from the institute have sent tissue samples of the creature to experts at UC Santa Barbara, the team will determine the creature's exact species, Press-Telegram reported.

The oarfish is believed to grow up to 49-feet-long, but the largest documented specimen was "only" 26 feet, Business Insider reported.

In June, and eight-foot-long oarfish was filmed swimming for the first time. The fish did not swim in the way scientists would have expected. Instead of moving its body side-to-side like an eel, the fish "hangs vertically in the water," Discovery News reported.

Researchers believe the oarfish doesn't have many natural predators because it fails to shy away from the lights given off by the video camera.

WATCH:

SEE OARFISH SWIMMING: