A SWEDISH team searching for booze on the bottom of the ocean may have found a UFO instead.

The Ocean Explorer team made several million dollars back in 1997 when it located the wreck of the trade ship Jonkoping.

On board was a consignment of 1907 Heidsick Monopole Gout Americain, the corks of which were popped late last year after wine buffs snapped up the bottles for around $13,000 apiece.

That's kept Ocean Explorer team leader Peter Lindberg in the deep-sea suds search business ever since, but nothing he's found has caused as much controversy as a circle that turned up on a sonar survey on June 19.

Mr Lindberg didn't say much about it at the time apart from releasing the image and ruling out theories that it may be a land mine or algae bloom.

Obviously, that didn't generate enough attention, so now, after further examination, Mr Lindberg has gone public with some more details about the dimensions of the disc.

"At 87m down, between Sweden and Finland, they saw a large circle, about 60 feet in diameter," he told local media last week.

"You see a lot of weird stuff in this job but during my 18 years as a professional I have never seen anything like this.

"The shape is completely round … a circle."

Mr Lindberg said the team has also noted what they say could possibly be tracks running some 300m up to where the disc lies.

The team claims the tracks show the object has moved, either on or since settling to the ocean floor.

Six of the nine-member team were asleep in their bunks on-board the Ocean Explorer's ship at the time of the discovery, but the three watching the sonar "couldn't believe" what they were seeing.

Despite the promise of alien riches, Mr Lindberg said his team would not attempt to investigate the disc.

"It is not in our sphere of interest to go for this object, since it might be nothing," he said.

"We cannot afford spending funds just to have a look at it, even if it might be a new Stonehenge."

"It is up to the rest of the world to decide what it is."