A group of up to 2,000 common dolphins has been spotted off the coast of west Wales.
Marine experts said it was "massively unusual" to see so many off the Pembrokeshire coast, and the reason remained a mystery.
Cliff Benson, who runs Sea Trust, the marine branch of the Wildlife Trust of South and West Wales, said it had been an incredible sight.
"It's fairly normal to see a hundred or so, but not thousands."
Mr Benson, who carries out regular survey work on cetaceans - dolphins, whales, and porpoises - was on his boat when he saw the dolphins approaching.
"It was like a volcanic eruption," he said. "There were dolphins of all ages - adults and mothers with their babies - and they were leaping out of the water.
"It's a mystery as to why there were so many. It could be because the waters are so rich in food, and that there aren't many predators.
"They could be coming here specifically to breed because the conditions are so right."
Mr Benson, who lives in Llanwnda, near Fishguard, is keen to get the Pembrokeshire coast marketed to tourists who enjoy seeing marine life.
"People think they have to go to Florida to see dolphins leaping out of the water, but it's all right here," he said.
"We should be marketing this area as 'The Dolphin Coast', and encouraging tourists to come here and spend their money to boost the local economy.
"There's a small coastal village in Ireland that has a particularly friendly dolphin, and people travel hundreds of miles to see him. He's worth £5m a year to that village."
Did you see the dolphins?
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We were at Tintagel Castle in Cornwall on 9th August and from the cliff we could clearly see dolphins leaping out of the water, they were very close to the shore and swimming South. I'm not an expert but both adults and calves seemed to be happy, playful and enjoying the glorious weather as I was.
Lynn Smith, Liverpool, England
Whilst doing a porpoise survey in July off Oxwich, Gower, we were delighted to observe a group of 250+ common dolphin. Not quite the thousands, but still a fairly unusual occurrence for this part of the coast. It was wonderful to watch them feeding and breaching for over 45 minutes before they headed offshore.
Rhian Jenkins, Swansea, UK
In 1992 whilst serving in the RN, I was off the coast of Spain when I saw a similar spectacle of over 2,000 dolphins. I called in to report my sighting to the survey team who were studying dolphins, and they didn't believe that I had seen so many. It's taken 13 years but I'm feeling vindicated.
Anna Sutcliffe, Halifax
I enjoyed the article and video of the dolphins. I wonder though if the shift to these waters is a suggestion that the equatorial waters are much warmer than normal and maybe are causing the dolphins to seek cooler waters further north than expected. We are increasingly arising on the east coast to temperatures in the 80s (Fahrenheit). Maybe the young cannot adapt to the change, or the swift westerly currents are driving them more north.
Ken Allport, Old Bridge USA
With that many dolphins, close to 2000, I think It's some sort of warning. They're swimming away from something for survival and I think that's a warning that something bad is going to happen. They have sensed it and moved away from it. We don't get that many dolphins, never have so why would they start coming over here now unless something drove them here?
Linda Williams, Pembroke
It would appear that the Welsh coast was not the only place that the dolphins gathered; a number of people from our island (located in the River Clyde on the west coast of Scotland) saw a large group of dolphins. They even played with the ferry from the mainland which had to make quite a large detour to get round them. It was quite a spectacle, as dolphins have not been seen much in the Clyde recently due to previously high levels of pollution. Maybe this is a sign that things are getting better.
Nick Beckwith, Rothesay, Isle of Bute, Scotland
I went to Wales for a holiday. It was my last day and I thought that it would be boring. It wasn't though. It is better than Florida itself. It was totally cool seeing hundreds of dolphins ripple through the calm waters. They were grey coloured. I always thought that dolphins were blue coloured
Angela, USA, Florida
I went down to the beach this morning (about 11.30) and there were at least five or six dolphins in the bay. Would these have been the same dolphins as seen yesterday?
Nicola Hughes, Benllech
I did not see any dolphins but my husband and I did spot a sunfish which is even rarer. We spotted the sunfish whilst fishing the mid channel rocks near Milford. It was approx one metre across.
Abigail Gibbins, Cardiff
We were in Port Isaac, Cornwall last week and on the evening of Monday 8th we saw what we assumed was a large group of dolphins. Unfortunately they did not leap out of the water and we only saw their fins, but having read this article, I am sure they were dolphins and quite possibly the same group seen off Pembrokeshire.
Nicola, Bedford, UK