About 25 long-finned pilot whales have been spotted off the Norfolk coast.
Carl Chapman, cetaceans recorder for Norfolk, said he saw the whales off Cley next the Sea on Monday and feared they were in trouble.
"They were initially very confused," he said. "They were breathing heavily and poking their heads out of the water to see where they were."
Mr Chapman said there was a moment when he thought they were going to beach, but they eventually headed out to sea.
"I phoned British Divers Marine Life Rescue to put them on standby, but thankfully they weren't needed," Mr Chapman said.
Mr Chapman said he counted 23 of the whales as they travelled east, but said there could have been a few more.
He believes it is the first time living long-finned pilot whales have been seen off the Norfolk coast, although there was an unconfirmed sighting in 2008.
The Cetacean Strandings Investigation Programme said it had been "somewhat concerned" about the risk of a "mass stranding event".
It said long-finned pilot whales were "occasional" visitors to the southern North Sea and their preferred prey was squid.
"The pod may not be feeding as normal and there may still be cause for concern for this group of whales," it said on Facebook.
The sighting comes just a few days after a humpback whale was spotted off the Norfolk coast, for the second year in a row.