A fire crew was called out to reports there were teenagers swimming in the River Trent.
Southwell Fire Station attended an area of the river near Gunthorpe, where crews said the youngsters were already safely out of the water.
But crew members issued a warning and gave advice on the dangers of swimming in the River Trent "despite looking calm and serene".
It comes as a spell of warm weather and sunshine is forecast for the week in Nottinghamshire and the concern some may see the river as a chance to cool off.
In a post on Facebook on September 15, the station said: "Another call out for T14P1.
"The crew were called to Gunthorpe after reports of teenagers in the River Trent.
"Thankfully the teenagers were found safe out of the water on arrival and have been educated on the dangers of swimming in waters such as the Trent.
"With the hot weather being forecasted in the coming days, we ask all parents be aware of what their children are up to and ensure they are educated on the hidden dangers the Trent poses, despite looking calm and serene."
