Water Safety New Zealand says lack of parental supervision is the main cause of the high number of pre-school drownings this year.
Six pre-schoolers have drowned so far this year, with the total number of deaths well up on the same time last year.
There were two at the weekend at the Waiwera thermal resort north of Auckland and in Moerewa in Northland.
Water Safety NZ general manager Matt Claridge says supervision is the major determining factor in the deaths this year.
He told Morning Report that parents need to keep a clear line of sight to their children or be in the water with them.