Incredibly, the current had carried it about 44km in 17 hours after it was spotted east of Montague Island.

The boat was towed back to Bermagui Harbour after being found upside down on Tuesday night, where it was pulled upright and is waiting for its owner to collect and repair it.

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The skipper who found it, Tony Lavalle of Ulladulla, said it was "like finding a needle in a haystack".

"But we got a little bit lucky and we found it," he said.

He said on Monday night he was asked by the insurance company for the catamaran to take his own ship Francesca and search for the missing vessel as it had been spotted off Narooma.

"I was quietly confident of finding it," Mr Lavalle said.

"But the freshness of the currents made me a little concerned."

He made some inquiries with fishermen in the area to work out the currents then went to the position that it had been spotted.

"I checked the tide and how it was going then we made calculations on how fast it was going and in what direction, and set out after it," he said.

"When we found it, it was right in front of our bow."

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It was located about five-and-a-half kilometres over the shelf from Tathra where there was a depth of 1500 metres.

Divers fixed ropes to the 11-metre long, eight metre wide vessel then they spent four or five hours towing it back to Bermagui.

Mr Lavalle said he was unsure about the chain of events that led to its capsizing off Port Hacking at Cronulla 10 days before it was found, but he knew all of its crew members had managed to escape safely.

While he has towed a few boats in his 35 years of fishing, he has never been tasked to find one before.

"I was very happy when I found it, I tell ya," he said.

"If we didn't find it that day we wouldn't have found it because it would have traveled out to sea."