Part of the Alcatraz myth was that the supposedly shark infested Bay waters ensured no escapees made it to the mainland. Well now here's video proof of that.

On Saturday, tourists on Alcatraz were greeted with a bloody scene when they witnessed a great white shark feeding on a seal just off the ferry dock. A large pool of blood appears in the video, taken by Chris Shindler, and shortly a shark makes its appearance, thrashing near the surface of the water. Some seal guts can be seen floating away when it all ends. "That's the best thing I've ever seen in my life!" says a young boy whose world was just rocked.

"This is the first recorded predation event I know in the San Francisco Bay," said David McGuire, Director of the San Francisco-based conservation group Shark Stewards and research associate at the California Academy of Sciences, in a press release. "It definitely looks like a white shark, about 8-10 feet from the phone video sent to us."

While great white sharks are usually associated with the open ocean, particularly the Farallon Islands, 27 miles offshore, they have been known to occasionally find their way inside the San Francisco Bay.

"For me its pretty exciting and a sign that the health is returning to the San Francisco Bay ecosystem," said McGuire. He also reassured that the risk of a shark attack on humans is always low, and adds, "I suspect this shark is well fed."