Barry Dock RNLI crews were called out to Sully Island, just off the Vale of Glamorgan coast, four separate times between July 3 and 4 to help people and their dogs who became stranded by the rising tide.
With warmer weather on the way, lifeboat teams are urging visitors to take extra care and plan visits around the tides.
Lisa Newberry from Barry Dock RNLI spoke to Claire Summers on BBC Radio Wales. She said: “People think ‘oh, its fine, its not high tide yet therefore I can just walk across because its only calf deep,’ but the water is just powerful enough to knock you off your feet and it’ll carry you into the channel really really quickly.”
The crossing between Sully Island and the mainland looks deceptively shallow during low tide, but can turn into a fast-moving channel in minutes as the tide rises.
Water in the channel can flow at around eight knots – faster than most people can walk and enough to sweep someone off their feet.
Ms Newberry said: “Nobody sets out to get stranded so regardless of whether its Sully Island or down the Mumbles, whether its at Porthcawl, it doesn’t matter.
“People don’t generally set out to get stranded. They’re just ordinary people who’ve just simply misjudged the tides or underestimated just how quickly the conditions change.
“On the weekend we were called out quite a few times, four is quite a lot in 24 hours.
“The key thing is that those people who got stuck, they didn’t actually try to swim across. They realised they were stuck and they made that 999 phone call, asked for the coastguard and we were there.”
To help prevent further incidents, the Sully Island Water Safety Team now monitors the causeway during peak times and advises visitors when it is safe to cross or return.
Visitors are warned not to cross to Sully Island three hours before high tide, and not to return until three hours after high tide has passed.
While signs – including an electronic display – are in place to warn about the cut-off times, these are sometimes missed.
The team ask simply that those venturing across “don’t let [their] day end with a lifeboat rescue.”
