The man charged with keeping people safe on Northland waters has revealed his top gripes about behaviour this summer.
Northland Regional Council Harbourmaster Jim Lyle said the issues arising again and again were people diving without warning flags and boaties setting out without proper lighting.
NRC rules meant anyone diving off a boat must display a blue and white flag, no smaller than 60cm square. This signalled passing boats to slow down to 5 knots within 200 metres of the divers' vessel.
"If vessels have divers out and don't have flags, and another vessel speeds past and divers surface, the result can be quite horrific," Mr Lyle said.
The other most common smack on the hand had been for boats without proper lighting.