A rarely seen deep-sea fish resembling a serpent was found floating dead on the ocean surface off the San Diego coast and was brought ashore for study, marine experts said.

The silvery, 12-foot-long (3.6-meter) oarfish was found last weekend by a group of snorkelers and kayakers in La Jolla Cove, north of downtown San Diego, in the U.S. state of California, the Scripps Institution of Oceanography said in a statement.

It’s only the 20th time an oarfish is known to have washed up in California since 1901, according to institution fish expert Ben Frable.

Scripps noted that oarfish have a mythical reputation as predictors of natural disasters or earthquakes, although no correlation has been proven.

Oarfish can grow longer than 20 feet (6 meters) and normally live in a deep part of the ocean called the mesopelagic zone, where light cannot reach, according to the National Oceanic and Atmospheric Administration.

Swimmers brought the La Jolla Cove oarfish to shore atop a paddleboard. It was then transferred to the bed of a pickup truck.

Scientists from NOAA Southwest Fisheries Science Center and Scripps planned a necropsy Friday to try to determine the cause of death.