An unusually large group of great white sharks has been spotted off the coast of California, according to an article on natureworldreport.com.

A U.S. Coast Guard helicopter noticed a school of about 20 great whites swimming about 100 yards off the shore near the city of Pacifica, just south of San Francisco on October 16.  Most of the sharks were in the 10- to 15-foot range, with a few being estimated at 18 feet.

Experts say the great white shark can grow up to 21 feet in length and a fully grown specimen can weigh as much as 7,000 pounds.  The sharks usually travel to the area around the Farallon Islands each year about this time to feed, before returning to the deeper parts of the ocean.

This news is coming after a video, shot on a cell phone last week showed a great white shark devouring a seal near San Francisco, received a good deal of notoriety.  The Coast Guard chopper was flying at about 500 feet in the air when the sharks were spotted.

It is estimated there are some 3,500 of this species of white sharks living in the world today, and about 220 of them hanging around in the waters off the coast of California.  The creatures are identifiable by their grayish skin on top and their white underbellies.  It is not unusual to see them swimming in groups, as they are social animals and often travel together in packs.

In addition to the waters off the coast of California, this species is most often found in Australia and off the South African coasts.

David McGuire of the nonprofit conservation group Shark Stewards said, “An unusual number of juvenile white sharks under 10 feet long have been observed this year, likely associated with the unseasonably high water temperatures along the coast.”

He adds, while shark attacks on humans are rare, “I might swim and surf somewhere else for a few days.”

Mary Jane Schramm, spokeswoman for the Gulf of the Farallones National Marine Sanctuary said, “This is the first I’d heard of near-shore aggregating in such an urban area.”

Officials are advising caution for the time being for people who want to swim, surf or kayak near the area.