A 'good Samaritan' had reported five children in distress at Endsors pool.
Two fire engines and a boat rushed to the scene but found the four youths to be fine.
A passer-by had phoned it in to Warwickshire Fire and Rescue.
Fire crews issued water safety advice to the children and the council warned residents not to swim in open water during the warm weather.
In a statement issued over the weekend, Warwickshire Fire and Rescue Services Community Fire Prevention and Arson Manager, Moreno Francioso said:
"I cannot stress enough the dangers that exist when swimming in open water. While reservoirs, lakes, rivers and other inland water may look safe and inviting, particularly on a hot day, there are hidden dangers below the surface that could seriously injure or even kill you.
“So please think twice before you get into deep water and not only put your life at risk, but also the lives of our firefighters or passers-by, who go in to try and rescue you.
"Several people have died in separate drowning incidents across England as the country experienced the hottest weekend of the year so far. The most recent incident on was on Sunday in Oxfordshire where a girl tragically lost her life after getting into trouble in a lake in Witney. These are horrific outcomes and we really don’t want to see that happening in Warwickshire. So please listen to our advice and stay away from open water!”