Two serious boat crashes have sparked a warning for boaties to be "ultra-vigilant" when towing thrill-seekers on the water.
An afternoon of fun turned to tragedy when a 36-year-old man died and another man was injured after two boats collided on Lake Ohakuri, southwest of Rotorua, about 4.15pm yesterday.
The incident came just two hours after five people, one a small child, were injured when two boats collided on Lake Middleton in Otago.
Both incidents involved boats towing sea biscuits - inflatable rings on which passengers lie.
Water Safety chief executive Matt Claridge said there were usually a couple of serious boat crashes during the summer holiday period because of congestion on lakes, rivers and waterways.
Boaties really needed to know the traffic rules so they were always in "the best place at the right time", he told APNZ.
"It's pretty difficult when you're towing someone behind the boat because you're looking forward, you're looking back.
"On the lake you can obviously drive in any direction you like, so you can get blindsided very easily. And when there's a lot of boats, obviously the likelihood of that occurring is far greater."
Mr Claridge said ultimate responsibility lay with the skippers.
"They need to be ultra-vigilant and they need at least one, probably two people on lookout, watching not only the skier but for other boats."
People being towed behind boats could also play a part by making themselves visible to other traffic on the water.
"Because you're bobbing in the water like a cork, it's quite hard to see if a boat's approaching.
"So whatever you've got - if you've got skis, a toboggan, a biscuit - you need to use that wherever possible as a means to identify yourself to any boats travelling towards you. Because often with the glare of the water, you can't be seen."
Police are still piecing together the circumstances behind the collision in which the Rotorua man died yesterday.
Detective Sergeant John Wilson of Rotorua police said the investigation, conducted with Maritime New Zealand assistance, was still in its early days.
The results would be passed to the coroner.
Taupo St John acting team manager Steve Lynch was reported as saying the man suffered major trauma to his head and neck and died at the scene, despite attempts to resuscitate him.
A second man, believed to be in his 40s, suffered minor injuries.
Mr Lynch said both boats involved in the incident had been towing biscuits when the crash occurred.
The death came just two hours after five people were injured in a boat crash on Lake Middleton, next to Lake Ohau.
Community Constable Bruce Dow of Oamaru police said one boat was pulling a sea biscuit and the other was being used for water-skiing when they collided.
Mr Dow said the young woman skiing behind one of the boats had tried to warn the driver about the imminent collision but was unable to be heard above the noise of the engine.
The two boats had met virtually head-on as both turned the same way to avoid the collision, he said.
A man in his 60s with a suspected broken leg and his three-year-old grandson, who suffered a head injury, were airlifted to Timaru Hospital.
A woman in her 40s suffered a suspected broken arm, a girl in her early teens suffered a knee injury and a boy in his teens had head and possible back injuries.
They were taken to Timaru Hospital by ambulance.
-Additional reporting by the Daily Post and the Otago Daily Times