The skipper of the Jeanette, Ernie Hayllar, told the inquest he'd known Mr Thomson about 10 years and although aware of his drinking habits did not detect the intoxication when they met at the wharf nor before they put to sea about 3.10am.
He said they'd been under way about 15 minutes when he noticed his lone crewman had, unusually, not put away the mooring ropes.
He pointed it out to Mr Thomson, and watched from the wheelhouse as Mr Thomson moved to carry out the task, but tripped and fell over.
"I thought this was unusual for him and that he was possibly not fit for work so decided to turn around, go back to port," Mr Hayllar said.
"Anyone who is a seasoned seaman wouldn't trip over a pound board on a deck."
Telling Mr Thomson to get inside, Mr Hayllar had turned the boat around when he realised Mr Thomson was no longer on board.
He stopped, then used the plotter to pinpoint the point at which Mr Thomson may have fallen, alerted the port harbourmaster and searched the area.
The body was found floating in the water at 8.16am amid searches involving police search and rescue, Coastguard, private vessels and a fixed-wing aircraft.
Mr Thomson and a friend had during the preceding evening drunk a 24-pack of beer stubbies, before going to the Union Hotel where they won $215 on the pokies.
According to friend Craig Miller's evidence they then had "quite a session ... we got stuck in and were having a good time".
About 2am, Mr Thomson became involved in an altercation and fell backwards and struck his head on the concrete and received a small graze.
Despite his interest in continuing the altercation, there was no further confrontation and Mr Miller took him to the boat.
Friends of Mr Thomson, and his partner told of his ability to hold his drink, without slurring or appearing intoxicated.
Mr Hayllar said that at the port he had not been close enough to notice alcohol on Mr Thomson's breath.
The Coroner said that although Mr Thomson could handle his drink it seemed he drank "rather more" than his typical 12 stubbies, and had shared "a couple" of joints with a cousin, but had not eaten during the evening.
There was no evidence as to when he may have consumed methamphetamine.
"In my view it is most unlikely that Kevin would have fallen if he was sober, and in the event he had fallen overboard sober he would have been in a position to take steps to save himself by staying afloat and calling for help," Coroner na Nagara said.
The Coroner noted he was also not wearing a lifejacket, but also that he was not required to wear a jacket while working, as opposed to if the vessel was sinking or afire.
The Coroner found the death was by drowning as the result of Mr Thomson's impairment by alcohol and drugs, but declined to make any comments or recommendations.
"I consider the risks of going to work on a fishing vessel while significantly impaired by drugs and/or alcohol are well known, and in this case the risks were realised."
