The Transport Accident Investigation Commission (TAIC) has launched an inquiry into a boating tragedy which left three men dead in Auckland's Manukau Harbour yesterday.
A team aims to recover any wreckage of the boat and to scour videos or photos of the incident.
A man, 23, was airlifted to Auckland Hospital and three bodies were recovered after a boat overturned near the notoriously dangerous Manukau Heads bar, yesterday afternoon.
Police said the three victims were men aged 54, 61 and 70. The fourth man is in moderate condition.
Police said they are continuing to work with Maritime New Zealand to "understand the circumstances leading to the deaths", and are making inquiries on behalf of the coroner.
The TAIC is appealing for witnesses who saw, photographed or videoed the boating accident. It's understood other boaties found three people dead in the water and rescued the fourth.
"Getting the facts straight is vital, so we're keen to hear as soon as possible from people who saw the accident or observed the boat at any time in its journey," said Harald Hendel, Chief Investigator of Accidents.
"Details of the boat involved are not known at this stage and this is where witness accounts may help, particularly if you have photographs or videos."
A dedicated team will be travelling to Auckland tomorrow to investigate. They want to interview witnesses and see any photos or videos taken of the incident. Investigators will also seek to recover any wreckage.
"We're interested in what people have to say, of course, particularly the survivor, but also what the families and friends of the crew knew about their plans for the trip," said Hendel.
"We're keen to find out more about the boat, its individual and type history, performance, maintenance, equipment and design."
Witnesses can email TAIC at firstname.lastname@example.org.
One local man who saw the recovery operation unfold 100m from his boat said the capsized vessel was "in the worst place in the harbour to be" and he is glad an inquiry has been launched.
"Some bigger boats that were already moored at Huia came out and gave [first responders] assistance," he said.
He followed a larger boat as it took the bodies back to shore and said emergency services performed CPR but they were pronounced dead.
The man, who the Herald has agreed not to name, said he helped clean up life jackets and other wreckage from the boat.
He said the mood was sombre back at the beach.
He had been among more than 200 boats who successfully crossed the Manukau bar that day.
"If you're going to pick a place where an accident was going to happen it was going to be that day on that bar.
"There would be another 100 [boats] that didn't radio in."
The deaths have been described by Coastguard as the worst tragedy on that body of water in many years.
Chief executive Callum Gillespie is urging Auckland boaties to be prepared, as hundreds of vessels - numbers matching peak summer levels - were seen out on the water yesterday.
Five people have died on Manukau Harbour in the past week. A diver and kayaker have also lost their lives since alert level restrictions eased in Auckland, allowing residents to participate in water sports.
"Three people dead in a single event is one of the worst tragedies in Manukau Harbour in a number of years," said Gillespie.
Coastguard teams from Papakura and Waiuku were deployed and searched "unsuccessfully" for the overturned boat.
Gillespie said the boat involved did not make a bar crossing report with Coastguard, but they did receive in excess of 200 bar crossing reports from the Manukau Harbour yesterday alone.
It was Coastguard's own "Super Saturday", with more than 1700 trip reports and 29 incidents, he said.
"That's a big day in the summer, never mind in October."
Most incidents were non life-threatening, involving flat batteries, people running out of fuel and mechanical failures.
But they showed many were not prepared to head out on the water.
"Understandably people have been locked up in the winter, through this lockdown period and their enthusiasm to get out ... is not unfortunately being matched by preparedness," said Gillespie.
He urged boaties to remember to check the weather conditions, pack lifejackets and two forms of communication, and to put in a trip report or bar crossing report with Coastguard.
"It's about making sure whether you're diving or kayaking or in a boat that your equipment is good and well checked and it hasn't rusted or become ineffective through the winter.
"If you leave your fuel sitting in your engine over winter don't be surprised if it doesn't work."
"Wear life jackets because when you're in the water it's too late to put the lifejacket on."
Coastguard is preparing for another bumper summer season with New Zealand's borders remaining closed.
Gillespie said boat trailer manufacturers are already being "worked off their feet".
"I think we're going to see a repeat of last year. It's going to be very busy.
"We are getting prepared for it and we would ask that Kiwi boaties do their bit by getting ready for it too."
The Manukau bar is notoriously dangerous and has led to a number of rescues, including two earlier this year.
Boaties can plan their trip here.
Safety tips for crossing the Manukau Bar
• Always check the swell, tide and wind conditions – every crossing of the Manukau Bar is different because of these factors.
• Always try and cross the bar during daylight hours.
• Make sure that everyone on board is wearing a lifejacket and is awake.
• Crossing at high tide is best (but always take the weather and swell into consideration too).
• Ensure that you are carrying two forms of communication that work even when wet.
• Log a bar crossing report with Coastguard by calling *500 on your mobile or contacting Coastguard radio from your VHF. Once over the bar safely close your bar crossing report.
• If in doubt, don't go out!