The body of Kevin Donald Croad (48), livestock worker, of Gore, was found yesterday afternoon after he went missing while fishing about 2pm on Saturday.
He had entered the water to untangle fishing lines which had caught on the boat's propellers, police said.
Wind pushed the boat - which was about 12m from shore on the lake's southwest corner - away from Mr Croad and although a friend threw him a paddle, he sank before he could be rescued.
Members of the Wellington-based police dive squad retrieved his body from the lake about 1.40pm yesterday as his family and friends watched from the shore.
He was found on the bottom of the lake at a depth of about 4m, about 3m from where he was last seen.
Detective Sergeant Derek Shaw, of Alexandra, said Mr Croad was not wearing a life jacket.
"If there is a lesson to be learned, it is that life jackets should be worn on all occasions when people go in or on water.""Although the death of Mr Croad is a tragedy, it is of some comfort to his family and friends that he could be recovered from the lake in such a timely manner.
It's a tribute to all the searchers involved that this result could be achieved," Det Sgt Shaw said.
The man's family and friends declined to comment yesterday.
Police are not sure whether Mr Croad died as a result of a medical event or from drowning.
"The matter has been referred to the coroner and we are keeping an open mind," Det Sgt Shaw said. Alcohol was not a factor, he said.
Mr Croad was part of a group which regularly travelled to Lake Onslow.
They arrived on Friday night and planned to stay the weekend in a fishing hut before returning home yesterday.
The group initially embarked on their own search for about 45 minutes before getting a cellphone signal and alerting police.
A diver and helicopter were dispatched from Alexandra before police arrived to undertake their initial search on Saturday, which was suspended about 6.30pm "when it was apparent Mr Croad's chances of survival were minimal", Det Sgt Shaw said.
Weather conditions were fine apart from a "steady, cool southerly"; the water temperature was only about 10degC, he said.
"We remained hopeful but realistic about his chances of survival . . . we were at 2500ft (762m) on a high country Otago lake.
It was very exposed and hugely susceptible to the weather, and there was a sense of urgency," Det Sgt Shaw said.
Five members of the Wellington-based police dive squad arrived at the lake yesterday to join the search, which resumed about 8am.
Det Sgt Shaw said members of Mr Croad's family, as well as friends, also arrived yesterday to help search.
Two Central Otago members of New Zealand Land Search and Rescue were involved, as well as two Central Otago coastguard members and four police officers from Alexandra, Roxburgh, and Ranfurly.
Last month, three South Canterbury men drowned on Lake Tekapo, and a fisherman also died on Lake Rotoma, near Rotorua.
None were wearing life jackets, Maritime New Zealand spokeswoman Sophie Hazelhurst said.
Maritime New Zealand was pushing for the wearing of life jackets to be made compulsory for boats under 6m, she said.
