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Mysterious Slugs Resembling Human Organs Wash Ashore in Northern California

Large sea slugs are washing up on Northern California's shores, much to the dismay of locals and tourists alike.

The creatures, also known as sea hares, can grow as large as 30 inches in length and weigh up to 15 pounds.

They're not foreign to California, but it is unusual to see them in the East Bay area.

"The California sea hare is common in southern California but is only found in northern California when there is warmer water, such as during El Nino years," Dr. Terry Gosliner, senior curator of Invertebrate Zoology at the California Academy of Sciences, said.

Water temperatures around San Francisco have been running about 4 degrees Fahrenheit above normal recently, according to AccuWeather Meteorologist Richard Jaworski.

"Normally, San Francisco's waters are around 57 degrees Fahrenheit at this time of year, whereas San Diego averages around 70 degrees Fahrenheit," Jaworski said.

Sea hares typically live away from the seashore at a depth of up to 60 feet, according to the Cabrillo Marine Aquarium in San Pedro California.

Though not a threat to humans, the creatures have caused quite a stir amongst beachgoers.

When threatened, the animals secrete a purplish, pinkish ink to scare off predators.

Their oozing ink and resemblance to the human heart has resulted in several panicked calls to local 911 call centers, CBS San Francisco reports.

"They're about the size of a human organ, and that's almost what they look like," Morgan Dill, a Naturalist with the East Bay Regional Park District, told the station.

This isn't the first ocean critter to wash up farther north than usual in recent weeks.

Last week, thousands of tuna crabs were turning beaches red in the San Diego area.

Usually seen in the warm waters off the coast of Baja, scientists believe warming waters farther north may be the reason for their unusual appearance.