New Zealand seaman Mark Ross drank 10 to 12 cans of full-strength beer before falling overboard from a seismic survey vessel while pretending to vault the safety rail, an inquiry has found.

An Australian Transport Safety Bureau (ATSB) report released today said crew members had consumed significant amounts of alcohol at a barbecue on the research survey ship Geosounder, in contravention of the owner’s no-alcohol “dry ship” policy.

The vessel’s Norwegian master – who had drunk about eight beers himself – had provided the alcohol as the 60m Norwegian registered ship sailed 185 nautical miles northeast of Cairns on August 25 last year.

The vessel was on its way back to its Singapore base, after doing exploratory work on the Brothers seafloor thermal vents on the Kermadec Arc northeast of Tauranga when Ross – one of eight New Zealanders on board – was killed at about 3am.

“The master gave his tacit approval for the consumption of an excessive quantity of alcohol by some members of the crew,” the ATSB report said.

Ross, 44, had over 25 years experience at sea, and was said to have been “skylarking” with fellow crew members after the barbecue when he pretended to vault over the ship’s handrail.

“As (he) pretended to vault the rail, his movement was amplified by the ships motion so that he overbalanced and fell over the port handrail and into the sea,” the ATSB found.

Two crew members tried to grab him but were unable to prevent him falling overboard, saw him fall and instantly threw lifebuoys overboard.

They quickly launched the vessel’s fast-rescue craft, but it was lowered by the captain and driven by the chief mate — neither of whom did those tasks in emergency drills.

The inquiry found crew members were improperly trained in the use of the rescue craft.

The report said the boat accelerated before it was released from the wire on which it was lowered, and stopped suddenly, breaking the ankle of another crew member.

“The hasty response of the crew bordered on panic.”

“It is possible (Ross) struck a narrow sponson (stabiliser) on the ship’s side during his fall overboard or that he was drawn through the propeller once he was in the water,” the report said.

“While he could swim, the alcohol that he had consumed would probably have inhibited his ability to swim or stay afloat once he was in the water.”

Ross was never seen again and the master called off the search about 15 hours later. Today’s report issued no recommendations or safety advisory notices.

Ross’s father, Bob Ross, of Waiheke Island, said at the time the family was angry the search had been called off relatively quickly.

“We don’t know why they called it off so bloody early,” he told the Herald on Sunday.

His wife Lisa told the newspaper that speculation that alcohol had been involved was upsetting: she said her husband had recently undergone chemotherapy to treat throat cancer and was unable to drink.