Firefighters have urged people to "swim with caution" ahead of the summer months as they highlighted the risks of open water swimming during a training exercise.
Humberside Fire and Rescue Service used the water outside Princes Quay shopping centre in Hull on Thursday to help prepare themselves for emergency situations.
Damon Li, watch manager at the fire station in Bransholme, said: "Getting into the warmer months, we tend to see a spike of people attending open bodies of water but it's important they know the hazards that come with that."
He advised those planning to swim in open water to "go in pairs, use What3Words and use the float to live technique if something goes wrong".
Mr Li staged a fake emergency response outside the shopping centre, in which four individuals entered the water after visiting nearby pubs and had led to only three casualties being visible.
He urged anybody who enjoys open water swimming to "act safely, let someone know you're going and enjoy it."
The fire service said it hoped to educate the public on "underestimated risks associated with open water" including hidden hazards beneath the surface, the danger of cold water shock – even on warm days – and how quickly cold water can become life-threatening.
Sarah Wilkinson, head of prevention at the fire service, said: "Our water safety campaign is all about equipping people with the knowledge they need to enjoy the water safely."
"Tragically, in recent years, young lives have been lost at local waterways, despite the heroic efforts of our firefighters and emergency service teams.
"As the warmer weather draws us to the water, it's crucial to understand the risks, particularly cold-water shock, which can have deadly consequences."
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