Tourists watch as great white shark tears apart seal at Alcatraz Island

A group of tourists witnessed the moment a great white shark devoured a seal carcass at Alcatraz Island in San Francisco Bay on Saturday.

The unbelievable sighting was captured on video and posted on YouTube, showing a pool of blood in the water as the shark ate the remains of the seal, just metres from the dock where the tourists awaited their ferry.

See also: Huge great white shark pictured swimming next to surfers

David McGuire, director of shark conservation group Shark Stewards and research associate at the California Academy of Sciences, said: "This is the first recorded predation event I know in the San Francisco Bay.

"It definitely looks like a white shark, about 8-10 feet from the phone video sent to us. The tourists were pretty excited."

See also: Incredible photos! Great white shark leaps out of water to catch seal in its jaws

In August, it was reported that experts believe more great white sharks are expected in the San Francisco Bay area after being pushed farther north than normal by El Nino.

Marine biologist Melissa Schouest told Kron4: "It's been really fascinating. We've seen the whole food web pushed up on shore for us to take a peek at."

In 2009, the San Jose Mercury News reported that researchers from Stanford University, the University of California-Davis and other organisations had found five great white sharks swimming underneath the Golden Gate Bridge between 2007 and 2008 after tagging 179 of white sharks in Northern California between 2000 and 2008.

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