A seven-mile-long mega-pod of around 100,000 dolphins delighted tourists - and the captain - on board a whale-watching boat off the coast of San Diego last week.
Captain Joe Dutra of Hornblower Cruises said he saw the "super mega-pod" of dolphins while on his daily tour last Thursday.
He said the pod was seven miles long and five miles wide, and estimated there were around 100,000 dolphins there.
Guests on board the cruise started screaming with delight when they saw the enormous school of dolphins swimming past the boat.
Mr Dutra told NBC San Diego: "They were coming from all directions, you could see them from as far as the eye can see. I've seen a lot of stuff out here... but this is the biggest I've ever seen, ever."
According to the BBC, marine mammal expert Sarah Wilkin said the reason the large pod might be there is because there's plenty of food in the area, including sardines, herring and squid.
She told NBC San Diego: "They're attracted to kind of the same thing, they might wind up in the same place."
Sarah said that although dolphins typically travel in groups of 200 or less, "super-pods" are not unheard of, adding: "They're definitely social animals, they stick together in small groups. But sometimes, the schools come together."
Mr Dutra described the sight as "truly spectacular".
Video: Tourists wowed as 1,000-strong dolphin pod overtakes boat
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