Footage of a superpod of hundreds of dolphins has been captured by marine biologists on board the Rosslare to Fishguard ferry.
The Wales-based Sea Trust was conducting its monthly survey on a Fishguard to Rosslare ferry when the common dolphins were spotted leaping from the water.
Sea Trust director Cliff Benson said the sea was "boiling" with dolphins in an "amazing" sight.
“They were coming from every angle and were leaping out of the water," he said.
The charity conducts monthly surveys from the Stena Europe ferry, and yesterday morning, about ten miles off the Irish coast heading towards Fishguard, they spotted the superpod.
"The lovely thing was it was a gorgeous sunny day and the sea was flat and blue," said Mr Benson.
"I had just got some new binoculars with an HD camera on, and suddenly the sea was boiling. It was amazing.
"I was trying to film, and people around me kept saying 'over there, over there'. They were coming from every angle and were leaping out of the water.
"They were just coming and coming. It was the last thing on earth I was expecting in the winter.
"We had at least 250 and that's a conservative estimate. I'm guessing there was as many as 500."
Although dolphin sightings are traditionally more common in warmer months, Mr Benson says Sea Trust has been spotting them all year round since about 2009.
Mr Benson added: "We would expect to see some nowadays in the winter, but this was just mind-blowing."