Safety warning after heatwave deaths - but what is cold water shock?

As many people across the UK seek relief from record-breaking temperatures by plunging into open water, the RNLI has issued warnings after multiple deaths in water-related incidents.

Nine people, eight of them youngsters, have died in water in the UK and Ireland during the latest heatwave, which has brought five days of unseasonably hot weather for spring.

Tuesday saw the hottest May day recorded in the UK, breaking the record for a second day in a row.

It led the RNLI to warn: "While the air temperature is warm, the seas are still cold and cold water shock remains a very real risk.

"With many school children enjoying half term, the lifesaving charity is urging everyone to stay safe."

What is cold water shock?

Cold water shock is how the body involuntarily reacts to a sudden immersion in cooler water, according to Water Safety England.

The shock causes the blood vessels in the skin to close, and increases heart rate and results in gasping, rapid breathing and being unable to swim, which can all lead to drowning.

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The RNLI says the effects of entering waters of 15C or below are "often underestimated", and "this shock can be the precursor to drowning".

It increases the heart rate, leading to blood pressure also going up, meaning cold shocks can cause heart attacks even in relatively young and healthy people.

Breathing rates can change uncontrollably and increase as much as tenfold, the charity says.

This can all contribute to a feeling of panic, which in turn increases the risk of inhaling water into the lungs.

"This can all happen very quickly: it only takes half a pint of sea water to enter the lungs for a fully grown man to start drowning," the RNLI warns.

"You could die if you don't get medical care immediately."

How to deal with cold water shock

RNLI recommends five steps under its Float To Live advice, which tells the public what to do if they were to get into difficulty in the water.

1. Tilt your head back and submerge your ears.

2. Relax and control your breathing.

3. Move your hands and legs to help you stay afloat.

4. You may find your legs sink, but that's OK as everyone has their own way of floating.

5. Practice to find your float while supervised.

Incidents during latest heatwave

The first reported incident involved 15-year-old Declan Sawyer, whose body was recovered after he got into difficulty after entering Swanholme Lakes in Lincoln on Sunday. Declan's father Carl paid tribute to a "funny and outgoing young man who loved his fishing and his football" in a statement via police, and urged parents, friends and family to "make their children aware of the dangers surrounding water".

On Monday afternoon, a 13-year-old boy died after getting into difficulty at Leadbeater Dam, near Halifax, West Yorkshire. A West Yorkshire Police spokesperson said the teenager was pulled from the water and taken to hospital, where he was pronounced dead.

That same afternoon, a man in his 60s died of cardiac arrest after entering the sea at Tregirls Beach, Padstow, to help two family members who had got into difficulty, Devon and Cornwall Police said. The two family members were brought to safety by members of the public.

On Monday evening, the body of a teenage girl was recovered from the water at Kingsbury Water Park, Warwickshire.

In the early hours of Tuesday, the body of a teenager was recovered from the water at Rother Valley Country Park near Sheffield after he went missing, South Yorkshire Police said.

Junior Slater, aged 12, also died on Tuesday after he got into trouble while swimming with friends in the River Ribble at Ribchester. His family described him as "our little blue-eyed boy" in a statement.

In County Dublin, Ireland, another teenager died while swimming in the sea over the weekend, officials confirmed on Tuesday.

On Wednesday, a body was found by rescuers searching for a teenager who went missing while swimming in open water in Cheshire. Specialist divers and helicopter crews were looking for the 17-year-old boy, who was last seen in the water at Pickmere Lake, near Northwich. Formal identification is yet to take place.

Another body was recovered on Wednesday after a multi-agency search for a missing teenager in Hawley Lake, near Blackwater, Hampshire and Isle of Wight Constabulary said.

Meanwhile, a 15-year-old girl is in critical condition after getting into difficulty at Formy Beach, Merseyside, on Monday.

(c) Sky News 2026: Safety warning after heatwave deaths - but what is cold water shock?