A 33-year-old was arrested this week after beachgoers told police he repeatedly drove his jetski close to the shore and among swimmers at a popular bay north of Auckland.
Police say they will take a tough line on maritime misbehaviour this summer to prevent people being harmed on or near the water.
The Weekend Herald has learned that several people called the police, concerned about Gulf Harbour man Lance Joseph's behaviour at Army Bay last Sunday.
They said he drove his jetski close to shore and among swimmers.
Police arrested Josephs on Monday, and he appeared in the North Shore District Court this week charged with disorderly behaviour.
He was remanded on bail until his next appearance, on January 22.
Police would not comment on the specifics of the case because it was before the courts, but said they wanted to issue a warning about appropriate behaviour on the water.
"Police will be keeping a close eye on the beaches this summer and remind people to keep to the rules and not exceed 5 knots within 200m of the shoreline," said Sergeant Jason Homan of Orewa station.
"We don't want to be dealing with any preventable tragedies on or near the water, and will take a hard line with people boating while intoxicated and not complying with boating regulations."
Waitemata police acting district commander Inspector Les Paterson said jetski ownership was growing.
"It stands to reason that the percentage of bad behaviour while riding these high-powered marine vessels will also grow," he said.
"Local authorities have been enforcing these issues but they have limited resources.
"But police have a message for irresponsible jetski riders - we can enforce the same laws as the regional council and even use more potent legislation in serious cases.
"We also have arrest powers. It's time to get serious about this, mainly because of the risk posed to innocent people." Mr Paterson said.
Maritime laws class jetskis as boats - with power, sail and jet boats, dinghies, kayaks, personal watercraft or waka.
Anyone water-skiing, diving, board sailing or fishing is also covered by the laws.
In December, Rotorua coroner Dr Wallace Bain also issued a stern warning to boaties to obey water safety rules this summer.
He said the time was coming when people would face more serious charges if they didn't start obeying the rules and someone was accidentally killed on the water.
• A person must be 15 to operate a jetski, dinghy or any power boat capable of speed exceeding 10 knots.
• All boaties must keep their vessel speed below 5 knots (walking speed) when within 200m of a shore, structure or boat flying a dive flag, and within 50m of another boat or person.