The chaos which ensued when a naval rating became trapped under the upturned hull of an inflatable seaboat being launched from the HMNZS Canterbury was disclosed to a coroner's inquest in Auckland yesterday.

Able Hydrographic Systems Officer Byron Solomon, 22, drowned in the incident off Cape Reinga on October 5, 2007, four months after the Navy took delivery of its new multi-role transport vessel.

Four sailors were on the inflatable for a launch training exercise when a boat rope used to keep the seaboat parallel with the ship released early in the moderate swell. The crew were then unable to release the boat from the davit wire used for the launch and the inflatable turned sideways, filled with water and flipped.

Two sailors were thrown clear but Mr Solomon and Leading Seaman Dwayne Pakinga were caught in strops securing the inflatable to its lifting hook.

Mr Pakinga told coroner Brandt Shortland that when the boat flipped he was trapped upside down by a strop. He managed to get his head above water and pull himself out. Once free, an exhausted and injured Mr Pakinga climbed on to the upturned hull.

Several officers had by then jumped from the still-moving Canterbury, defying standing orders, and were trying to free Mr Solomon. An attempt to activate the boat's self-righting apparatus failed.

Petty Officer Mark Taylor found Mr Solomon unconscious and tried to pull him from under the inflatable but the pair kept getting dragged under. On board the Canterbury, it took officers several minutes to cut the davit wire using a hacksaw to release the boat, by which time the Canterbury had slowed to a stop.

Two inquiries found design flaws and incorrect equipment contributed to the tragedy and the Navy changed both its launch equipment and the seaboats.

Outside the court, Mr Solomon's father, Bill, said the equipment was clearly a hazard.

"The oval link attaching the craft to the hook wasn't built to design: they realised that it hadn't been built to design, they realised that it was difficult to use and I think probably - although it hasn't been stated categorically - they recognised a hazard."

Mr Solomon was disappointed the inquest would not focus on this issue.

Additional reporting: NZPA