A jetskier captured on video speeding narrowly past a river cruise boat could face prosecution.

Charter boat skipper Percy Ginders said the incident on Ngunguru River, now being investigated by the Maritime Safety Authority, was the closest call he'd had in 16 years of operation. It happened to be captured by a passenger filming a Monday morning family outing.

"He [the jetskier] would've killed himself. Fortunately, he was able to avoid me, but only by a whisker," Mr Ginders said.

Northland Regional Council's Navigation Safety Bylaw means all watercraft need to travel at 5 knots or less within 200m of shore or 50m of another boat.


"That waterway is for everyone," Mr Ginders said.

"Imagine if there could have been kayakers. He made no allowance for other people whatsoever."

There were seven adults and one child on board the eight-metre charter vessel when the near-miss occurred.

"I'm always very wary, but no one would ever guess that someone would be so stupid," Mr Ginders said.

Passenger Richard Hawkins captured a six-second clip from the bow showing the charter boat approaching a fork in the river, when the jetskiing man careened round a corner, coming within metres of the boat, amid screams from passengers.

Northland Regional Harbourmaster Jim Lyle confirmed a complaint had been referred to the Maritime Safety Authority, which had been able to identify the jetski owner using the video clip and a jetski registration system introduced about five years ago.

They were in the process of contacting the driver.

"The penalty could be anything from a bylaw fine to prosecution under the Maritime Transport Act," Mr Lyle said. "The person in the clip was certainly doing more than 5 knots - but that's all I can really say at this stage."

Mr Lyle was surprised, as a registration system, a collaboration between councils in Northland, Auckland and the Waikato, had in general improved jetskiers' behaviour.

Mr Hawkins had been out with several family members and described the near-miss as "a real shock".

"Afterwards, everyone on board was stunned, even the captain."

He shared the video online to create more awareness of why obeying the rules was important.