A Kaeo firefighter who is also a member of St John, 17-year-old Nadia Martin, spoke to ambulance personnel and others at the scene.
"From what I gather two girls aged about 14 noticed the men were in trouble and went in to help them," she said.
The girls, understood to be southerners on holiday in Northland, had got hold of one man each and shouted for help.
Three boys aged 17 or 18 had gone out with a surfboard, which was used to get all nine people back to shore.
Ms Martin said the rescue helicopter had flown three of the men to Bay of Islands Hospital in Kawakawa to have their condition checked.
The fourth man and the three boys followed in the Doubtless Bay ambulance and the two girls were taken to the hospital in the Kerikeri ambulance.
Northland District Health Board staff said all were treated and discharged.