West Yorkshire Fire and Rescue Service (WYFRS) is warning that despite seeming like a good way to cool off on hot days, the shock of can be fatal in open water.
It comes after a teenage boy died in the water at Greenbooth Reservoir in Rochdale on monday, the hottest day of the year.
And in Yorkshire, two girls were rescued from Sparth Reservoir, near Marsden, on Sunday after nearly drowning in the water.
WYFRS’ Martyn Greenwood said: “We are very saddened to hear about the tragic loss of life of a youngster at Greenbooth Reservoir, Rochdale, and our deepest sympathies go out to his family.
“There has also been concerning news in Kirklees, Yorkshire, of the near drowning of two girls who reportedly got into difficulty at Sparth Reservoir near Marsden on Sunday and were rescued by three adults.
"The Fire Service was not called to this incident however we are eager that the Summer months are approaching and with more good weather on the way, young and old alike should be aware of the dangers of open water.”
The advice is being issued during national Drowning Prevention Week, which is run by the Royal Life Saving Society UK, and is taking place this week.
Around 400 people die from drowning every year in the UK, as a result of an accident in or around water.
Firefighters from Rastrick Fire Station will be at Ogden Water, Halifax on Friday, carrying out an exercise to raise awareness of the dangers of open water.
WYFRS is also promoting the Float to Live summer safety message from the Royal National Life Saving Institute (RNLI).
The RNLI have released a video featuring advice on how to react should if people are stricken in cold water.
Advice on open water and cold shock
The RNLI says everyone who falls unexpectedly into cold water wants to follow the same instinct, to swim hard and to fight the cold water.
But cold water shock can cause you gasp uncontrollably and breathe in water, which can then quickly lead to drowning.
If you find yourself unexpectedly in the water, the RNLI advises people to float until the cold water shock has passed, when you can then control your breathing and have a far better chance of surviving.
For more safety advice, visit www.wyfs.co.uk/news/fire-service-issues-summer-water-safety-advice