"I would say stampedes are one of those most amazing things I've seen in 20 years of whale watching," said Anderson, who estimated 500 animals were captured in the video. "It's completely exhilarating."
Porpoising — when dolphins repeatedly leap from the water — is their fastest mode of travel, allowing them to move at speeds of up to 20 knots, or nearly 25 mph, Anderson said.
"Everyone screams at first, and then everyone is totally silent. All you can hear is a just a really loud splashing sound. It's kind of like being in a herd of stampeding horses, but you are not afraid you will get stepped on," Anderson said.
There are an estimated 450,000 common dolphins that swim off the coast of Southern California, Anderson said.