Yorkshire Water and Yorkshire Fire and Rescue Service have backed a campaign to 'Be water Aware' after more than 120 reported incidents of swimming in Yorkshire Water's reservoirs in the last 10 months.
The National Fire Chiefs Council have said that 223 people accidentally drowned in the UK in 2019, with 44% of those deaths happening in lakes and reservoirs.
Yorkshire Water said they have seen a "worrying" increase in the number of people swimming in reservoirs during lockdown.
Gaynor Craigie, head of land and property at Yorkshire Water, said: "Entering a reservoir is dangerous. Low water temperatures can cause cold water shock that may lead to hyperventilation, increased blood pressure, breathing difficulties and ultimately death.
"Underwater machinery and the currents associated with their operation are also a potential hazard for people choosing to enter the water."
The "Be Water Aware" campaign is part of a national strategy to cut water-related deaths by 50% in the next five years.
Lee Miller, district officer for Wakefield at WYFRS added: "We know that everyone is making the most of the warmer weather and the changes in restrictions, and it’s great that we’re all starting to feel some element of normality again.
"However, when it comes to visiting open water, we’re joining Yorkshire Water and the NFCC in asking people to be water aware – cold water shock can kill, as can many of the other risks that open water poses."
He added: "Please, if you are enjoying the beautiful countryside that West Yorkshire has to offer, please do so safely.
"And importantly, remember that if you or someone needs help call 999 and ask for the Fire Service immediately – our crews are trained and equipped to deal with such incidents."