Plunket is urging parents and other caregivers to keep an extremely close eye on children around water this summer.
National adviser Karen McGrath said many families are spending time at swimming pools, beaches and rivers.
But Ms McGrath has warned that things can go wrong very quickly if children are left unsupervised - even for a moment.
"They can drown in as little as five centimetres of water so that's only the length of our little fingers.
"[It's] really important to avoid distraction, know who's supervising the children so it's a good idea to make that a real clear purpose," she said.
Ms McGrath said people should tip rainwater out of buckets and unattended paddling pools, as they also pose a risk.
She added that if families are having trouble finding healthcare over the summer break, Plunket can help.
"If you are away from your GP, you're worried that your child might not be well, you can ring us.
"We can do an assessment, we'll help you and we'll guide you to where your nearest local doctor will be from wherever you are in New Zealand."