The man who drowned at a popular Canterbury tourist spot was diving to collect seafood when he went out of sight for around an hour.
He was 43-year-old Chen You, from Halswell in Christchurch.
Police were alerted about 1.15pm on Saturday after a person was pulled from the water by the harbourmaster at Akaroa on Banks Peninsula.
A witness at the scene said it was immediately clear the situation was serious.
鈥淲e heard sirens from quite a distance away from shore, and the person was already on board the boat,鈥 she said. 鈥淭hey were lying flat and receiving CPR.鈥
She said people ran along the pier as emergency services arrived within seconds and took over resuscitation efforts.
Despite CPR being administered, the person could not be revived, a police spokesperson said.
鈥淥ur thoughts are with Chen鈥檚 family and friends at this time.鈥
The death has been referred to the coroner.
It comes after a spate of water-related deaths across the country.
Cousins Johnathan Brian Webster, 54, of Dargaville, and Joseph Wiremu Webster, 43, of Tauranga, died after they were pulled unresponsive from the water at Ripir艒 Beach on Kaipara鈥檚 west coast on the evening of January 3.
The two men were seen struggling in the surf between Mahuta Gap and Glinks Gully.
One-year-old Laylah-Mae Thompson died five days after falling into a pool at her home in Wairarapa.
Teananga Tiotia, 25, of Hamilton, died after he went missing in the Waikato River for nearly three days.
Police were called to the river near Graham Island on Saturday after a report of a 鈥渟truggling swimmer鈥 being swept downstream.
His body was recovered on Tuesday, with the family notified.

Akaroa Wharf's Drummond pontoon. Photo / Christchurch City Council
Water safety advice
Earlier, Water Safety New Zealand chief executive Glen Scanlon urged people to keep in mind the key messages around water safety at this busy time.
鈥淲hat we tend to see is so often those hot, calm days when people find themselves unexpectedly in more trouble because the conditions look so good,鈥 Scanlon said.
He advised Kiwis to never swim or dive alone in any of New Zealand鈥檚 water environments.
鈥淚f you鈥檙e at a patrolled beach, please swim between the flags. Take advantage of the great surf lifesavers and the job they do to keep you safe.
鈥淧lease, if you鈥檙e fishing from land or from a boat as well, wear a lifejacket. It鈥檚 going to keep you really super safe.
鈥淚f you鈥檝e got your kids, always stay close to them,鈥 Scanlon said.
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