Parents are being urged to avoid distractions such as phone calls and browsing social media when supervising toddlers around water, with the risk of drowning tripling after a child's first birthday.
Royal Life Saving Australia says 41 per cent of drownings among kids under five occurred in one-year-olds, with 202 recorded in the past 17 years.
It said no other age was at greater risk of drowning, with the Australian Bureau of Statistics listing it as the number one cause of death in one-year-olds.
Most of those drownings - 59 per cent - occurred in backyard swimming pools.
Royal Life Saving said "almost all" the deaths were due to lack of adult supervision.
"Parents and carers need to know that the risk of drowning triples as soon as a child starts to crawl, peaking shortly after a child's first birthday," CEO Justin Scarr said on Wednesday.
"We can't emphasise enough how important active adult supervision is in preventing these deaths. Distractions are dangerous - whether it is taking a phone call, browsing social media or ducking inside to grab something - we ask parents and carers to always keep watch.
"In addition, it is essential that people install pool fences and check pool gates regularly to make sure they are not faulty or kept propped open."
The state with the largest number of one-year-old drownings was NSW with 67 deaths in the past 17 years, followed by Queensland with 56.
Western Australia recorded 33 drownings, Victoria 24 and South Australia 15.
AAP