A couple have told about an "extraordinarily powerful" surge in a Welsh sea harbour where the tide went into reverse due to a rare phenomenon.
Charles and Claire Davies, whose home overlooks Solva harbour, in Pembrokeshire, saw what is known as a "meteotsunami" where the sea suddenly rushed in and out at high speed last Saturday.
"The water appeared to be running out of the harbour rather than in," Charles told WalesOnline.
"We started to see this strange event where the water was surging in and out and in again. This happened a number of times over the next quarter of an hour."
The retired engineer, 69, continued: "There was a gentle north-easterly wind, the trees were hardly moving, it was a lovely sunny day. We expect surges during storm conditions but we've never seen one during benign conditions.
"We saw water coming in at seven knots, going back out again and causing boats to lean quite dramatically. It was causing an area of swirling water, a back eddy around the little headland.
"If there were people in the water swimming or in kayaks, it would have been quite a serious event to them, because an Olympic swimmer swims at five or six miles an hour and this water was moving considerably faster than that, I would say. They wouldn't have been able to keep up with it."
Charles said the "extraordinarily powerful" surges died down after about 15 minutes and in his 13 years living in the area, he said he had never seen anything like it.
But then one of Charles' family members heard about a similar tidal event which happened at 2pm on the same day in Cork.
One charter boat operator at Courtmacsherry harbour said he could see the water was "going the wrong way, it should have been coming in," reported the Irish Times.
He added: "The water was rushing out like a river. I’d never seen anything like it before. The first thing you think is ‘tsunami’ and to be honest if it was going any faster I think we all would have been heading for the hills.”
Experts believe the activity may have been caused by a meteotsunami — large waves driven by disturbances in air pressure, often linked to extreme weather events.
Oceanographer Dr Gerard McCarthy told the Irish Examiner that Courtmacsherry was regularly affected by seiching, an oscillation of tidal currents — "basically water moving backwards and forwards".
He added: "My best guess is that this regular seiching coincided with a dramatic and sudden change in atmospheric pressure somewhere out over the Atlantic off the coast of West Cork.
"If you imagine someone dropping a large volume of water straight down on the sea, that’s the kind of effect we are talking about. That pressure combined with the regular to and fro of water in those bays could have created a dramatic and unusual effect like the one we saw.”
The expert believes the same atmospheric event could have had an impact in Wales and this explains the Solva activity.
"It definitely had an impact, though less severe, further along the Irish coast in Wexford and there is also evidence of it being felt in Wales and Cornwall so this was quite a significant event," he said.
