Several outlets report that at least 12 people have died after swimming in open water across the UK during the current heatwave. The fatalities have led to renewed public warnings about “cold water shock,” a rapid reaction that can occur when a person suddenly enters cold or cool water. Sources describe the risk as particularly acute because the body can involuntarily gasp or begin hyperventilating, which may make it harder to stay afloat or swim. The reports also highlight that cold water shock can affect even when air temperatures are high, since water temperatures may remain significantly cooler. While the specific circumstances of each death are not detailed in the provided summaries, the coverage converges on the same message: people should understand cold-water risks before entering open water and take precautions to reduce sudden temperature shock. Both outlets frame the deaths as a warning for swimmers and other people who might enter lakes, rivers, or the sea during hot weather.