Torea was on a fishing charter on August 12 when it struck a rock off Ruapuke Island about noon and began taking on water.
Skipper Peter Leask beached the boat on Ruapuke Island while his two crew prepared the life rafts and issued all 24 passengers with life jackets.
Everyone was rescued from the island uninjured later the same day.
In its report, released yesterday, the Transport Accident Investigation Commission said Torea was permitted to carry only 20 passengers and Mr Leask was not aware there were 24 on board.
Investigators were told that soon after leaving Bluff, he asked one of his crew members to find out how many passengers there were. The crew member asked the fishing trip leader, who said there were 20.
The commission said investigators had been unable to contact the trip leader, who did not respond to attempts to contact him.
''It is difficult to comprehend that the trip leader did not know how many passengers he had arranged for the trip.
''Nevertheless, it was the skipper's responsibility to ensure that his vessel was carrying no more than the permissible number of passengers.''
Carrying more passengers than permitted was a ''serious safety issue'', as it could affect the vessel's operating limits, life-saving equipment requirements and crew-to-passenger ratios, the commission said.
''Additionally, should a catastrophic event occur, the search and rescue response will not know how many people are involved.
''Valuable time can be lost trying to reconcile how many were on board against how many have been rescued.
''Delays in retrieving people from the water can result in serious injury or death.''
The commission made no further recommendations against Mr Leask or Torea owner-operator Campbelltown Seafoods Ltd, saying the company had changed its charter booking procedures to ensure no more than 20 passengers were carried on future trips.
All bookings were now made through the company office, the names of all passengers had to be given to the company at least one day before a charter trip, passengers were required to have photo identification, and only passengers with identification whose names were on the list were allowed on board.
The commission concluded the collision with the rock was a risk that had been ''reasonably mitigated'' by Mr Leask, although it noted it could possibly have been prevented had Mr Leask travelled at a slower speed until clear of the shallow area known for the existence of ''uncharted dangers''.
The hull of Torea, which was built in the 1940s, was split in the incident and extensive damage was caused to the interior and equipment when the boat filled with water.
Its soft landing place brought problems for New Zealand Diving and Salvage director Dougal Fergus. However, with the help of a bucket digger and 40 tonnes of ballast, the boat was successfully lifted and returned to Bluff Harbour a week after the near sinking.
Mr Leask, who is also an engineer and shipwright, supervised repair and upgrade work costing more than $150,000. The work was completed in time for Torea to rejoin the Bluff oyster fleet when the season opened in March last year.
Mr Leask could not be contacted for comment yesterday.
-allison.rudd@alliedpress.co.nz
Main points
• Skippers must know how many people they have on board and ensure the maximum permitted number of passengers is never exceeded.
• It is risky operating small craft in shallow areas that have not been fully surveyed, so skippers must proceed with the utmost caution at minimal speed to avoid colliding with uncharted dangers.
