Two fishermen may have died after a simple turnbuckle broke when their net snagged, rolling their prawn trawler in the dark, in heavy seas off Queensland.
An inquest into the deaths wound up on Wednesday, also hearing that ropes stowed with lifeboats may have stopped them deploying - in a cascade of catastrophes in the sinking of FV Cassandra on April 4, 2016.
The bodies of skipper Matt Roberts, 61, and crewman David Chivers, 36, have never been found and it is presumed they were in the wheelhouse when the boat rolled.
Expert witness Barry Ehrke, who was commissioned by Maritime Safety Queensland to report on the sinking, says it's likely there was a net "hook-up" on the ocean floor before the vessel capsized.
Naval architect Doug Matchett gave evidence that ropes and rigging stowed near the Cassandra's life rafts could have stopped them launching as designed when the boat rolled.
"Certainly that should be a free area around the life raft," he told the Gladstone inquest on Wednesday.
Despite carrying the correct safety equipment, none of it worked.
Neither of the two emergency radio beacons were activated and the two automatically deploying life rafts remain on the boat, found in 47 metres of water - too deep for divers - off the northern tip of Fraser Island.
Video of the wreck shows the boat, upright on the seafloor, with two life rings.
The inquest is exploring whether the vessel was structurally sound, if there was adequate safety equipment, and if the search and rescue operation was sufficient.
Huge swells prevented rescuers reaching the stricken vessel, which is believed to have rolled after one its nets snagged on rocks or reef.
Mr Ehrke, a retired fishing boat owner and industry advocate, said the vessel should not have been in the notoriously rough stretch of ocean 10 kilometres off Waddy Point.
"In that area there's a lot of current and there's numerous hook-ups on obstacles on the bottom," he said.
In those conditions, the Cassandra's net set-up, which hung from the end of its seven-metre boom arms, was too unstable, Mr Ehrke said.
When the inquest began on Tuesday, the boat's former manager Dennis Markwell painted a bleak picture of the Cassandra's prawn trawling operation.
He had welded shut an emergency exit and contracted an unqualified boatbuilder to refit the fishing boat as a four-net prawn trawler, without discussing the potential ramifications of the massive top-heavy weight.
The boat's owner, Paddockmist Pty Ltd, had no knowledge about the safety requirements and didn't provide its crew with safety training, the inquest heard.
The safety management system lacked key information on dealing with net "hook-ups" on the sea bed, despite having been ordered to have it by Maritime Safety Queensland.
Similar issues will be explored in relation to FV Dianne, which sank with the loss of six lives on October 16, 2017, when the inquest resumes on Tuesday next week.
Australian Associated Press
