Five men died and a sixth person is thought to be missing in another seaside tragedy as Britons basked in the sun on the hottest day of the year.
Beachgoers and emergency services tried to save three of the men after they got into difficulties in the water at Camber Sands near Rye, East Sussex, at around 2.15pm on Wednesday.
Two more bodies were found at around 8pm as the tide receded, and the RNLI and Coastguard were combing the sea and shoreline for another person thought to have been spotted in the sea.
The deaths bring the toll to 12 in less than a week as people head for the coast at the tail end of the school holidays.
Two-year-old Mckayla Bruynius died at Bristol Children's Hospital on Tuesday night after she was caught by a large wave at Fistral beach in Newquay, Cornwall, on Friday.
Her father, Rudy Bruynius, was also killed after getting into trouble as 13ft waves lashed the coast amid strong winds and rain.
A mother and son died on Saturday after a rescue operation at Aberdeen beach, while a windsurfer in his 60s died in a Colchester hospital after being rescued off the coast of West Mersea, Essex.
On Sunday a woman in her 30s died after getting into difficulties while swimming off Jersey, before a man died despite the efforts of medics after getting stuck in a rip current at Sandbanks beach in Poole, Dorset.
People took to the beaches across the UK on Wednesday as thermometers recorded the hottest day of the year, with health officials warning people to take extra care of themselves and vulnerable friends in the blistering temperatures.
Temperatures hit 33.9C (93F) at Gravesend in Kent, topping the 33.5C (92.3F) recorded at Brize Norton in Oxfordshire on July 19.
With more people flocking to the UK's beaches as a mini-heatwave hits the country, the RNLI has urged seaside visitors to take care and respect the water.
A spokeswoman said: "The sea may look appealing, and the RNLI would encourage people to use it, but do so safely - it can be dangerously unpredictable.
"Please visit lifeguarded beaches and swim between the red and yellow flags - the safe swim zone and the area watched by lifeguards.
"RNLI lifeguards are always happy to answer any questions or advise of any risks, including where any rip currents may be, which can catch out even the most experienced swimmers."
The new high for 2016 spurred bookies to slash odds on it being the hottest summer on record, with Coral offering 2/1.
The Met Office issued a level three heatwave action alert for the South East and eastern England - triggered when threshold temperatures are reached for one day and the following night.
The alert means there is a 90% chance the maximum threshold temperature for the region - 30C (86F) in the East, and 31C (87.8F) in the South East - will also be met the following day.
A level two alert has been issued for the East Midlands, meaning there is a 60% chance the maximum threshold temperature of 30C will be met.
Emma Sharples, a Met Office meteorologist, said the hot weather was down to a combination of strong sunshine and extra warmth being pushed northwards from the continent.
But there will be a respite from the heat in the coming days as temperatures fall a little, with some cloud and rain bringing fresher conditions.
Explaining the heatwave, Ms Sharples said: "We are drawing on the continental flow from France and Spain, where they have been having equally high and higher temperatures as we have seen today.
"As we go through the next couple of days that changes subtly and we will see some cloud and showery rain around, which will cool things off."
Thursday will still be quite warm in the South East, with temperatures reaching the mid-20s, while across the rest of the country thermometers will register around the low 20s.
Showers overnight will push northwards from the south coast, and while rain will only be sporadic it could be heavy in localised areas.
The weekend will see a "mixed bag", Ms Sharples said, with cloud and rain coming in from the South West on Saturday, before turning brighter and clearer on Sunday.
Bank Holiday Monday is expected to be the best day of the long weekend, with sunny spells and temperatures reaching the mid-20s, along with the odd isolated shower.
Bookmaker Coral is offering odds-on at 1/2 that August will be the hottest ever, and has it at 5/2 that the record high temperature of 37.5C (99.5F) is broken this year.
Coral's John Hill said: "The odds suggest by the time this month is out, it will have been the hottest August in history in the UK, while the gamble behind this summer being the hottest on record is showing no sign of stopping, leaving bookmakers sweating over a big pay-out."