The warning follows an incident earlier this week where youngsters were found swimming in the water of a disused quarry in the area of Colne Golf Club.
A spokesman for Colne and West Craven Police said: "Parents, do you know what your children are doing? It has been brought to our attention that children have been swimming in the water of a disused quarry in the area of Colne Golf Club. Now that the weather is finally warming up, we understand how tempting it might be to go for a swim, but we ask you to please remind your children of the dangers of open water.
"We really do not want to have to attend any reports of children getting in to difficulty in this type of situation as the consequences are, all too often, tragic.
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"Here are some bonus tips for staying safe around water:
Never swim anywhere with a no swimming sign.
Never swim if you have been drinking alcohol or using drugs.
Never allow children to swim unsupervised in rivers, quarries or lakes."