Like some kind of cetacean flash mob, an enormous pod of dolphins was spotted this week off the coast of California near San Diego. Capt. Joe Dutra of Hornblower Cruises told NBC 7 that the pod was more than seven miles long and five miles wide. By his estimate, there were up to 100,000 dolphins.

In January, a pod of about a thousand dolphins was seen off California's Dana Point. While dolphins generally travel in small groups, this mega-pod behavior is thought to occur when several pods congregate to follow a food source, like sardines or herring. Whether or not they call each other together to swarm is unknown, but scientists say that once together, they are very likely communicating.

“When you see something that is honestly truly beyond belief,” Dutra told NBC.

NBC’s Diana Alvear from NBC reports:

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Massive pod of dolphins seen near San Diego
Scientists say they were very likely communicating with each other.