Water Safety New Zealand says parents need to make sure they empty their temporary pools when they are not in use.
A one-year-old baby drowned in a pool set up in a backyard in south Auckland yesterday.
The infant was the eighth preschooler to have drowned this year
Water Safety New Zealand's chief executive Matt Claridge said people should not take the risk of leaving pools unattended.
"It only takes two inches of water to drown and it can happen in less than a minute, so mum and dad, you just need to be absolutely certain that you want to take that risk and my advice is that you don't even bother."
Mr Claridge said temporary pools should be emptied and stored away if they were not being used.
Overall, 84 people have drowned this year.