Coastguard New Zealand is calling on boaties to be vigilant around evolving sand bars after two separate boating accidents on the Coromandel Peninsula.
Three people - including two children - are in a critical condition after a serious boat accident on the Coromandel Peninsula.
The incident occurred at Tairua bar near the coastal town of Pauanui.
Earlier this week, a boatload of people had a lucky escape when their vessel flipped on the same body of water.
Coastguard New Zealand is now warning people to educate themselves about navigating waters instead of thinking they know the lay of the land.
"Talk to locals who know the land" - Coastguard NZ operations manager Rob McCaw
Coastguard New Zealand's operations manager Rob McCaw told Morning Report people need to keep themselves informed on changes in their local boating environment.
"The risk with the Tairua, Pauanui bar is the sands have shifted quite significantly and there has been a lot of silting there over the last period of time and that really hasn't been addressed," he said.
McCaw said Tairua bar now has sections so shallow in an outgoing tide that any swells put people at risk of nosediving into the sandbar.
"Tairua bar has not claimed the most lives around the country in respect to bars but what everyone needs to understand about a bar is that it's always changing.
"You have to be current in what that bar has done, how it's grown or evolved over the last period of months, weeks or even just straight after a storm."
McCaw encouraged boaties to talk with locals who know the land and observe the tides before heading out on the water.