The Papakura cousins that set out fishing on Thursday morning were not wearing life jackets when their 4m runabout capsized in the Firth of Thames, between Coromandel and Waiheke Island.
By the time two survivors were seen clinging to the upturned hull yesterday morning they had been in the water 20 hours. A third was found nearby struggling to stay afloat.
A 13-year-old boy is still missing while his three family members are in a stable condition in hospital - and frustrated police are pleading with people to take basic safety precautions.
The boy and the others, two in their 20s and one in his late 30s, clung to the boat in the dark but somehow the teenager drifted away in the night. His family were aware he was gone but were unable to do anything.
Sergeant Graham Jex of the police maritime unit said there were lifejackets on board - but not worn - and the group didn't have a VHF radio but cellphones, which proved useless when they went into the water.