A police officer dived to rescue a child from under a boat after it capsized off the East Coast of Wellington Harbour on Sunday.
A police spokesperson said the 4.8-metre boat had launched from Lowry Bay and began experiencing worsening sea conditions while travelling along the Eastbourne coastline.
When the skipper slowed down, the waves began to spill over the boat's stern. Deciding to turn the boat around to return to shore, the boat capsized, throwing four adults into the water.
The only other person onboard, a child wearing a lifejacket, was trapped in the boat's cabin space where an air pocket had formed.
The adults thrown from the boat were able to push the boat towards the shore, where police arrived to meet them.
While the occupants and bystanders attempted to upturn the boat, a police officer dived from an inflatable into the water and rescued the child from the vessel.
Wellington Police Maritime Unit sergeant Richard Kennedy said it was a relief no one was hurt.
"Thankfully no-one was seriously injured or worse during this incident," Kennedy said. "The skipper stated that everything happened so fast. We're relieved this had a positive outcome, but it could have been so much worse."
Kennedy said it was frustrating how many of the maritime unit's call-outs could be easily avoided.
"We are still seeing people out there on the water without lifejackets, or children not being supervised, so there's nothing or no-one there to help if they get into trouble.
"We're talking about things like keeping an eye on children when they're on the water, putting a lifejacket on, knowing the marine weather forecast, avoiding alcohol while doing water activities, keeping within your limits and generally treating water safety as a priority.
"Tragedy doesn't discriminate and if something goes wrong, it could happen before you can react."
Police said the boat which capsized was equipped with lifejackets and flares, and its occupants were wearing either lifejackets or wetsuits - which can be a suitable alternative.
Maritime New Zealand compliance deputy manager Scott Bernie said this was a clear example that "lifejackets save lives".
"Skippers should not leave the shore if they are not adequately prepared to go out on the vessel they are in charge of. Overconfidence can be one of the biggest risks on the water," Bernie said.
Maritime New Zealand recommended water goers undertake water safety courses available through the Coastguard or seek advice at [www.saferboating.org.nz the safer boating website].