Officials are urging Derbyshire residents to take extra care near open water - as the summer holidays start and temperatures soar.
Open water includes areas such as flooded quarries, ponds, reservoirs, rivers, canals and the sea.
Around 85 per cent of accidental drownings occur at open water sites and many of these are due to a lack of knowledge and understanding of the hazards these sites pose.
Young people in particular are attracted to open water - and although it may look safe and inviting particularly in hot weather, even strong swimmers can get into difficulty within a matter of moments.
Derbyshire Fire and Rescue Service has produced the above video to highlight the dangers of open water.
We are sharing Derbyshire Fire & Rescue Service’s video “Shock” to highlight the dangers.
Inspector Lauren Woods, of Derbyshire Constabulary, said: "We are urging people to stay safe over the summer by making themselves and their children aware of the risks of open water.
"When the weather is warm, it is tempting to jump in to cool off, but this can endanger your life and the lives of others if they then enter the water to help you.
"There are still plenty of things to do safely near open water sites and we don't want to discourage people from enjoying the activities some sites provide - but please be safe and stay out of the water unless you know the site is properly supervised."
Dan Taberner, visitor experience manager at water provider Severn Trent, added: "We want everyone to enjoy the lovely weather which is why it's so important for everyone to keep safe at our sites, and that includes staying out of the water.
"Although our reservoirs look tempting when it's hot, the fact is they're extremely dangerous.
"On the surface they look calm and steady but, underneath, the water is extremely deep with incredibly strong currents that even the most experienced swimmer would struggle with.
"On top of that, we don't have lifeguards or safe swimming areas, so we really do need everyone to keep out of the water."
He added: "Not only are our reservoirs really deep, they're also extremely cold.
"If you go into any of our reservoirs, you might end up in serious trouble and, unlike beaches and swimming pools, there are no lifeguards to help you - so please don't take the risk."