Public Health Wales warns of dangers of cold water shock when jumping into open water in the heatwave 

Published on: 25 Jun 2026

Public Health Wales is asking people to be aware of the dangers of cold water shock in the current heatwave, and say that people should enter the water gradually at first.   

Cold water shock happens when people jump straight into cold water rather than getting in slowly and allowing their bodies to acclimatise to the lower temperature. 

The shock results in people taking big gulps of air and inhaling water, their breathing rate increases rapidly and their heart rate spikes, and they can get into difficulties very quickly.

While air temperatures are exceptionally high during the current heatwave, water in large bodies of water such as lakes and the sea is still very cold at this time of year.   

Professor Sarah Jones, Consultant in Environmental Public Health, said: “We are really concerned that cold water shock could become an issue as people look to cool off from the very hot temperatures. 

“Lakes and the sea do look inviting in this weather, and open water swimming is a good way to cool down, but it’s really important to get into the water gradually so that you’re able to acclimatise to the difference in temperatures. 

“You should only use areas that are safe to swim in and go with someone else.  Never swim if you have been drinking alcohol or using drugs.  It’s also a good idea to be aware of the RNLI advice on how to Float to Live (external site). 

“I would ask parents and carers to ensure that they know where their children and young people are, and to tell them to take these simple precautions so they are able to enjoy swimming in the open water.”