The Department of Labour and Maritime New Zealand will not investigate the circumstances surrounding the death of an American tourist in the Marlborough Sounds.
American tourist, Emily May Harper, 27, of Denver, Colorado, was swimming with the dolphins in Tory Channel on a Dolphin Watch EcoTours trip when she was found floating face down in the water on October 20.
The tourist boat came into Waikawa Marina and was met by a coastguard vessel with a paramedic on board, but the woman had died.
Department of Labour spokesman Colin Patterson said the department would not be investigating further.
"It's our belief that the woman died of natural causes."
He said the death was a police matter.
Maritime New Zealand spokesman Ross Henderson said investigators went to Picton to find out if they should look into the incident, but found it did not fall into their jurisdiction.
Coroner Sue Johnson said the provisional post-mortem suggested Miss Harper did not drown, but died of natural causes.
However, she was waiting on blood tests, including toxicology results, before making a final ruling on the cause of death.
The autopsy results are expected within the next six weeks.
Meanwhile, it has been revealed that Miss Harper's partner, Matthew Hawkins, waved a multitool (a pocket knife) at paramedics when it became apparent they could not save her.
Senior Constable Brett Parkinson, of Picton police, said Miss Harper's fiance, Matthew Hawkins, picked up a multitool, which he used to cut Miss Harper's wetsuit.
Mr Parkinson said the man became increasingly agitated as he watched his partner die and started waving it around.
"I don't think he knew what he was doing himself."
Mr Parkinson said the man did not threaten anyone else. He freely handed the multitool to police.
St John regional operations manager Chris Haines said it was rare for staff to come across aggressive patients or bystanders.
He said officers made allowances for patient and bystander emotions, which could run high.
- The Marlborough Express