I was on a whale-watching trip Wednesday aboard the Legacy off San Diego when dolphins stole the spotlight in spectacular fashion.

We had just observed a southbound gray whale that did not stay near the surface long enough for quality views, so our captain ventured farther offshore.

We saw common dolphins in the distance, beyond Point Loma. But they, too, moved lazily atop a calm ocean during an unseasonably warm afternoon.

But as we approached, still a few hundred yards away, the dolphins changed behavior as if they had been activated by a switch.

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Typically, dolphins greet approaching boats and bow ride or leap playfully in their wakes. These dolphins seemed frantic, porpoising to the south in a powerful, unified effort to vacate one location in favor of another – as swiftly as possible.

Perhaps 1,000 dolphins, including babies alongside moms, high-tailed at top speed.

We followed parallel for about two minutes before the dolphins stopped stampeding and began to appear alongside the Legacy to ride its bow and surf its wakes.

Scientists are not sure why dolphins stampede except for obvious reasons, such as predatory orcas in their midst.

They could become spooked by something else, such as unusual sounds or disturbances that only they can detect.

Stampeding could also simply be a mass relocation mechanism for feeding purposes, or a social behavior.

We did not see orcas or anything unusual besides active military vessels and aircraft.

The dolphins stayed with the Legacy for several minutes before we had to return to port.

We saw another “uncooperative” gray whale on the way back, but it was anticlimactic after what we had just witnessed.

This article originally appeared on For The Win: Dolphins stampede by hundreds in unexplained phenomenon off San Diego