Mr Partridge had been at Furneaux Lodge on Monday night playing pool and "having a few beers'' with his daughter and her boyfriend.
Bar staff say the trio were going to stay the night on their 14-metre launch tied to the jetty.
It appeared they then decided to leave the lodge, and were motoring through Endeavour Inlet, probably bound for the man's bach at Marine Heads, near Ships Cove, when the father fell in about 2am.
He was not wearing a lifejacket, police say.
His daughter and her boyfriend raised the alarm and a search was launched.
Furneaux Lodge owner Geoff Faulkner, who was staying in Nelson, said yesterday that the man - who was not a regular - had been staying at his bach in the Sounds when the three of them boated to Furneaux to "play pool and have a few beers''.
"It was just a quiet Monday night. I've spoken to the bar manager. Nothing untoward happened in the night,'' he said.
Asked if alcohol could have been a factor, Mr Faulkner said: "We don't believe they had that many. The barman who walked them down to the boat didn't think they were drunk.
"It just looks like an awful tragedy, after deciding to take the boat out. It's a horrible, terrible thing.''