It was a rare, breathtaking sight: In a flash, a pod of about 1,000 common dolphins began a stampede, churning across the blue-gray waters off Dana Point at a rapid pace.

Dave Anderson, the captain of Capt. Dave's Dolphin and Whale Safari, said that in the decades he's spent on the water and out among Southern California's dense dolphin population, it's a phenomenon he's encountered only rarely.

Yet last weekend, it happened again ... and it happened twice: once on Saturday afternoon and again on Sunday morning. Boat hands captured Sunday's stampede on video.

"It's one of those things you can hope for it, but you can't plan for it," he said.

"It's one of the most amazing things I've ever seen, and I've seen a lot of beautiful and interesting things" on the water.

He described the sensation like being in the midst of a herd of wild horses. The dash began in an instant, he said. At some points the dolphins reached speeds of more than 25 mph, outpacing his boat.

"Suddenly, like someone fired a gun," he said, "they're off and running."

He has tried but has yet to come up with an explanation for what prompted the rush: "Are they afraid? Are they chasing after something? Why are they doing this?" he said.

"We don't know. I know they're not running away from the boat. It seems like they're responding to something but I just don't know what it is."

The sight, he said, could be seen from miles away. But to be in the middle of it was surreal.

"It's very exciting and very freeing," Anderson added. "It's quite a magical experience."