Backyard pools can be a welcome relief from the summer heat, but they also pose a danger that can prove deadly if care isn’t taken.

Injury prevention specialist Jane Harrington says no matter how many times you've heard about the importance of staying safe around water, it can't hurt to hear the message one more time.

Both children and their adult supervisors, Harrington told CTV London, can get so excited around water they forget to heed the rules that can keep them safe.

"Parents get a little lax about keeping them within arms' reach," she said.

Harrington works at the London Health Science Centre, located in one of the few Canadian municipalities that requires homeowners to erect a barrier around the perimeter of their backyard pools.

Under the London, Ont. bylaw, one side of the barrier can be the outer wall of the house or a deck. That, critics say, means children can still potentially gain access to the pool.

Quebec passed a law in 2010 making it mandatory for all newly built pools to be entirely surrounded by a fence on all sides, while pools installed before the law came into effect remained subject to local bylaws.

In fact, local bylaws prevail across much of the country, with Manitoba being the only other province with pool enclosure rules on the books. Under the Manitoba Building Code, pools must have a barrier, but it does not have to be four-sided.

A provincial pool enclosure law was also proposed in Ontario, but did not pass into law.

Whatever the laws are in your neck of the woods, safety experts say there are some common guidelines that apply wherever pools are found.

According to the Middlesex-London Health Unit, the four keys to safety around water are:

  • supervising young children around water
  • keeping kids within sight and arms' reach
  • taking swimming lessons and learning first aid
  • ensure young children wear personal flotation devices at all times

Harrington cautions, "that doesn't mean toys and pool noodles, that means an actual safety device."

And beyond the confines of backyard pools, Harrington says people relaxing near lakes and rivers need to be aware of the dangers that could be lurking beneath their apparently calm surfaces.

"You don't realize that that water can be especially dangerous for young swimmers who get pulled under that water," she said, referring to the powerful hidden currents, or undertows, that can drag unsuspecting swimmers down.

The ensuing panic, she said, can sometimes prove tragic.

And don't forget, the experts say, that one can drown in less than three centimetres of water. That means kids, whose smaller lungs can quickly fill with water, must be constantly supervised even if they're just frolicking in the shallows of a wading pool.

According to the injury-prevention organization Safe Kids Canada, there are several "layers" of measures people should take to keep children safe around any body of water including:

  • Constant adult supervision, from within arm's reach especially when watching children aged five and younger
  • Training for adults, from CPR to swimming, as supervisors who can't help youngsters in distress can do little more than retrieve a child and call for help
  • The use of barriers, which can range from physical, four-sided, minimum 1.2-metre tall fences around backyard pools, to clear rules for activities around open bodies of water
  • Young and weak swimmers' use of lifejackets approved by at least one of Transport Canada, the Canadian Coast Guard or Fisheries and Oceans Canada
  • Swimming lessons, as a means of building both skills and confidence around water.

With files from CTV London and Safe Kids Canada