Firefighters and community rangers are worried about the number of people swimming in lakes and other waterways in Milton Keynes.
Figures provided by The Parks Trust, who carry out daily patrols at sites with a history of incidents, have shown that dozens of people are ignoring water safety warnings every week.
The biggest concern is at Caldecotte Lake, which lies off the H10 Bletcham Way, between the V10 Brickhill Street and the A5.
Groups of people have been seen swimming near the Anglian Water weir structure on Caldecotte Lake North, and the jetties belonging to Milton Keynes Sailing Club on Caldecotte Lake South.
Chris Bailey, head of Buckinghamshire Fire & Rescue Service’s community safety team, said: “Now the warmer weather is here, you might be tempted to take a dip in rivers, lakes or canals.
“But please think again - people are easily caught out by hidden dangers like deep holes, soft mud, weeds or rubbish.
“Strong currents or cold water can quickly overwhelm us and pollution or algae can make us ill. You are much better off going to your local swimming pool.
“Parents have a special responsibility to warn children of the risks and know where they are when they are out playing.
“Never let children take dinghies, airbeds, tubes or other inflatables on to water. Set them a good example - act responsibly near water, and never swim, even where allowed, after drinking alcohol.
“At home, keep small children away from ponds and swimming pools and make sure they are supervised in the bath.”
If you see people swimming in lakes and other waterways, ring Thames Valley Police on 08458 505 505.
Buckinghamshire Fire & Rescue Service has two Water Safety Units, one at Newport Pagnell Fire Station and one at Beaconsfield Fire Station. Each is equipped with a boat and specialist water rescue equipment and staffed by highly trained swift-water rescue technicians.