The incident happened at Tinker Bridge around 11.30am on Sunday, July 27, when the youngster was playing with friends.
It is believed he struck his head on an object as he fell into the water, causing him to suffer a serious head injury.
Inspector Sue Sanderson, who leads the Keighley Area Neighbourhood Team, said that people needed to be aware of the dangers of playing or swimming in open water.
Insp Sanderson, said: “On a hot summer’s day, open water like streams, rivers and canals can look inviting. But these waterways are not swimming pools. There are no lifeguards in case someone gets into difficulty and there can be hidden currents which can catch out even an experienced swimmer.
“The temperature of open water is often very cold and this can also cause difficulties. People suddenly entering cold water are susceptible to hyperventilation, which could result in the body going into seizure and possible drowning.
“Water rescues can also put the lives of emergency services staff at risk. Compromising their own safety to help others is often part of the job, but situations like this are wholly avoidable.
“We want people of all ages to enjoy a safe and pleasant summer, but this shows how easily accidents can occur. Please stay safe and stay out of the water.”
The message is also being echoed by Yorkshire Water, which has warned the public to stay out of its reservoirs.
Geoff Lomas, Recreation and Catchment Manager at Yorkshire Water, said: “Reservoirs are extremely dangerous due to the chilling temperatures and the potential for strong under currents beneath the surface.
“What began as a day out in the sunshine can turn to tragedy within minutes if you decide to take a dip. It really doesn’t matter how well you can swim as it’s the cold which can kill you.
“Most people won’t realise that, as soon as your body feels the shock of cold water, it’s natural defences kick in. The first sign of trouble is hyperventilation but, if the swimmer stays in the water, the body will gradually shut down to protect the vital organs and muscles will got into cramp.
“The victim will be unable to remain afloat and will sink below the surface and, if help doesn’t arrive within seconds, they will drown.”
Yorkshire Water advises all those visiting its reservoir sites over the summer months to enjoy the scenic views and to pay particular attention to all safety signs.
West Yorkshire Fire and Rescue Service Manager Ian Thompson, who is a Technical Rescue Officer, said: “Too often in the past people have been drawn to the cooling waters on a hot day, only to find that they are simply not capable of functioning in the low temperatures encountered in the deeper water.
“Often this results in a call to the emergency services and in some instances with a fatal outcome. Time is crucial when it comes to helping someone in trouble, if you see someone in distress in the water dial 999 immediately.”
Vince Larvin, Locality Director of Emergency Operations at Yorkshire Ambulance NHS Trust, said: “Yorkshire’s many waterways are popular destinations for people during the summer months, which can make them dangerous places for those who don’t understand the risks they are taking.
“It may be very appealing to jump into the reservoir to cool off on a warm summer’s day but people need to be aware of how dangerous this really is.
In June, a 38-year-old man died after swimming in Snailsden reservoir in South Yorkshire, the latest in a series of deaths at the company’s sites.