Swimming warning following boy's death
Philip Law, 15, drowned a fortnight ago after getting into trouble
while swimming in Manvers Lake with two friends.
to see anyone else hurt or injured from swimming in open water."
A police spokesman said that there are many dangers of swimming outside due to cold temperatures, depth changes, currents and insecure banking.
Open water should only be swum in at properly organised events, they said, when lifeguards are on duty.
Steve Makepeace, South Yorkshire Fire and Rescue's head of community safety, said: "Traditionally, call-outs for open water rescues increase at this time of year, as people attempt to cool off and then get into difficulties in the water.
"Open water presents a number of different hazards. Although it may look tempting during hot spells, it is impossible to gauge its temperature, flow or depth."
Alan Baranowski, assistant director of A&E Operations for Yorkshire Ambulance Service, added: "Water can look calm on the surface but contain unseen debris and rivers in particular can have treacherous undercurrents.
"Reservoirs have automatic equipment located under the surface, which can operate without warning and cause dangerous hidden currents.
"The temperature of deep water is much colder than people expect and, even on a hot summer's day, rarely gets above freezing.
"This is cold enough to take your breath away, which is the body's natural reaction and cannot be controlled, possibly leading to panic and drowning."
Cold could also make the arms and legs so numb that a person could not control them to swim, he added.