The Laval drowning of a one-year-old boy in a bathtub has prompted Quebec's Lifesaving Society to remind parents that it only takes 15 to 20 seconds for a toddler to drown, in as little as a few centimetres of water.

Laval police said a mother left the baby and his two-and-a-half year old sister unsupervised in the tub for just a few minutes in the family's home in the Auteuil district of Laval on Sunday evening.

When she returned to the bathroom, she found the boy had slipped under the water.

The mother gave the infant mouth–to–mouth resuscitation, and he was rushed to hospital, but he died later that night at Sainte-Justine Children's Hospital.

Police are investigating but said the death appears to be an accident.

Laval police Sgt. Stéphane Pilon hopes other parents can take a message away from the family's loss.

"You have to stay in the place when the baby takes the bath," said Pilon.

That message is echoed by the executive-director of the Quebec Lifesaving Society, Raynald Hawkins.

"Don't give the responsibility to older sisters or brothers," Hawkins said.

He said parents should maintain eye contact with their young children every moment they are in the tub. To avoid distraction, they should bring everything they might need into the bathroom before they run the bath – towels, pajamas, even a cordless phone – so that there is never a reason to leave a child unattended.