The Australian Maritime Safety Authority says it has no reason to doubt two Burmese men who say they drifted in a large fishing esky for nearly a month before they were found by a Coastwatch plane in the Torres Strait.

The men in their 20s say they were on a 12-metre Thai fishing boat with 18 others when it sank in rough seas two days before Christmas.

The men say they last saw the others swimming in open seas without life jackets.

The Authority's Tracey Jiggins says it is an incredible story.

"That is the story that we have been given by the two survivors. Both of them have been very adamant about their story so we can only take their story on face value and follow through on the information they have provided to us," she said.

"Other authorities; Immigration, the Department of Foreign Affairs will now follow through on other aspects of this."

Helicopter pilot Terry Gadenne helped rescue the pair, and says it was a textbook procedure.

"We winched him up and got to the other fellow soon thereafter and they were both desperate to get some water in," he said.

"They were certainly thirsty. They put down two litres of water really quickly each. They had some boils or damage of some sort to their legs and that was given first aid and we flew straight to the hospital from there."

The two men remain in hospital at Thursday Island in far-north Queensland.

Ms Jiggins says the men were spotted by a Coastwatch plane on Saturday floating in the commercial fishing esky.

She says it is unlikely there are other survivors.

"There were other people onboard the vessel at the time, they saw two groups of crew; one of 11, one of seven go down with the vessel and neither group had any flotation device with them," she said.

"With the time that has gone by it would be unlikely that there would be any survivors from the vessel if they were in water with no floatation devices."

She says there will not be a search for more survivors.

"We understand the vessel was boarded in Thailand and that the crew onboard were Thai and Burmese and we consequently notified all the relevant Australian authorities that will notify the government of those two countries," she said.

The Immigration Department is trying to verify their identities and will speak to the men again.

Thursday Island tour operator Greg Edwards told ABC Radio's AM program seas in the area have been treacherous.

"Very strong north-westerly winds maybe gusting up to 50 knots and squalls moving through the place," he said.

He says the men are lucky to have survived their ordeal.