Big waves and no lifeguard cover could create a “perfect storm” of danger for beachgoers, rescuers have warned.
Waves up to 16ft (4.9m) high are forecast to hit beaches in the south west on Friday and Saturday.
Steve England, of surfing magazine Carve, predicted the conditions and the “loosening of lockdown restrictions could be recipe for disaster”.
The RNLI has warned that none of its lifeguards are currently patrolling UK beaches.
There was a surge of visitors to coastal areas this week, with reports of people travelling great distances to the seaside and “gridlock” in resort towns.
Mr England warned that tourists could be caught unawares this weekend by tidal surges and rip tides and were liable to get out of their depths.
He called on experienced surfers to “keep an eye out for potential victims”.
Tom McRitchie, 23, an RNLI lifeguard and patrol leader with rescue charity Surf Life Saving (SLS), usually patrols at Perranporth, Cornwall.
He said he was aware of holes in the sand which meant people could be up to their necks in water with just one wrong step.
“The lockdown has been relaxed, the weather is good and there’s a big swell on the way so for those who are caught out in the water, it’s a perfect storm,” he said.
The SLS, which is looking for sponsors to fund equipment, is asking members to volunteer as “beach wardens” to monitor and report incidents to the coastguards and lifeboat crews.
“I feel a bit helpless in a way,” Mr McRitchie said.
“I know the dangers so not being able to do the job is frustrating.
“It’s a weird situation not being able to do the job I love.”
There have also been a number of rescues in the last week by off-duty lifeguards.
Lukasz Kowalski helped a 10-year-old boy who had been swept off his feet, through pounding 4ft shorebreak and into a rip current at Chapel Porth, Cornwall.
‘Lucky I was there’
The boy was brought back to shore unharmed by Mr Kowalski, who happened to be in the water taking photos, on Wednesday.
“The number of people is going to increase because the weather is beautiful,” he said.
“People just want to get out and they don’t think about safety.
“He was lucky I was there.”
Adam Richards, chairman of Porthtowan Surf Lifesaving Club in Cornwall, was surfing when he spotted a young boy and his father caught in a rip current on 16 May and brought them back to the beach on his surfboard.
“As there wasn’t a flagged bathing area set up, there was no indication on the beach of the safe place to go into the sea,” he said.
“There is going to be some big surf this Saturday.
“I would advise people… please don’t go in the sea unless you know what you are doing.”
The RNLI, which would normally be two weeks into its main season, is rolling out a reduced lifeguard service “in phases” from the end of the month.
In conjunction with the Coastguard, it has launched a joint water safety campaign reminding families it “cannot be everywhere this summer”.
“We are working with local authorities and landowners to provide a lifeguard service on beaches as quickly as possible,” said a spokeswoman.
“Setting up a lifeguard service on any beach takes time, while we have done as much as we can to prepare during lockdown, there was limit to what we could do under the government’s restrictions.”