A whale-watching trip off San Diego turned into a rush of fins, spray, and sound when a mega-pod swept across the Pacific near the U.S.-Mexico border. Professional wildlife photographer Domenic Biagini filmed the encounter, which showed thousands of dolphins moving at high speed across the surface, Newsweek reports.

The scene soon spread online. The clip has drawn more than 3.2 million views since first being covered. Aerial footage showed a wide band of animals in near-unison, not a loose cluster.

A whale-watching trip off San Diego turned into a rare view of thousands of dolphins.

The Sound Was Part Of The Shock

The moment was not quiet. People reported that the group was estimated at 2,000 to 7,000 common dolphins, far above a typical pod.

Storyful noted that a voice behind the camera first questioned the roar before calling it a stampede. Biagini told Storyful that a normal common dolphin pod often sits closer to 100 to 500 animals.

The dolphins moved as one across the Pacific.

Why Dolphins Form Huge Pods

Scientists do not point to one cause. In this case, Biagini told Newsweek that orcas were in the area. Dolphin stampedes can also start when animals race toward prey, flee a threat, or move as part of a social burst.

Matador Network explains that these events often occur near food sources, with dolphins using porpoising to gain speed above the surface. Dana Wharf Whale Watching points to three broad drivers for superpods: heavy prey, protection from sharks or orcas, and social contact among smaller groups.

The stampede created a roar loud enough to startle people on a boat.

California Waters Can Hold Vast Dolphin Gatherings

The scale fits a coast where common dolphins can gather in huge numbers. NOAA Fisheries says short-beaked common dolphins off the West Coast can form mega-pods of thousands, with some groups reaching up to 10,000 animals. The agency also notes their surface behavior, including fast leaps and bow riding near ships.

Large gatherings have surfaced elsewhere in California. In February, a Monterey Bay captain filmed more than 2,000 dolphins, including northern right whale dolphins and Pacific white-sided dolphins, AP News reported. That pod was about 11 miles from harbor, with calves visible among the adults.

A Rare View Of A Fast Wild System

The San Diego stampede did not need a single neat explanation to matter. It showed how quickly the Pacific can shift from blue distance to living force.

For the people on the boat, the shock came from scale. For everyone watching later, the power came from the same fact: thousands of animals made the ocean sound alive.