Australian man Lewis Bennett, at the centre of a mystery after his new wife vanished from their catamaran near The Bahamas, will make an attempt for freedom at a bail hearing in Florida later this week.

Bennett, 40, was locked up in a Florida jail after his arrest on Monday for allegedly stealing valuable gold and silver coins.

The FBI declined to say if they were also investigating Bennett for the disappearance of his Colombian-born wife Isabella Hellman on his 12-metre catamaran as it sailed from Cuba to Florida in May to celebrate their honeymoon.

The couple's one-year-old daughter was not on the catamaran.

According to documents filed in the US District Court related to the theft charge, Bennett said he was asleep at about 1am on May 14 when he heard "a loud thud", the catamaran started to sink and he could not find Ms Hellman, who had been at the helm.

"Bennett indicated he was unable to slow the flow of water, so he gathered his personal belongings, deployed his life raft and abandoned ship," FBI special agent James Kelley wrote in the criminal complaint.

A US Coast Guard helicopter picked up Bennett, but the rescue swimmer who pulled him out of the water allegedly noticed a backpack the Australian-UK dual citizen had "was unusually heavy".

The backpack was not searched but another bag left in his life boat allegedly contained 158 "English Year of the Horse" silver coins and 77 "Canadian Maple Leaf" coins.

Authorities later discovered the owner of a boat on which Bennett was working in St Maarten last year had $US100,000 in gold and silver coins stolen.

A search of Bennett's Florida apartment allegedly discovered 162 gold coins hidden in a pair of boat shoes.

Bennett, formerly of Queensland, has been charged with transporting foreign commerce known to have been stolen.

Just a day after a search for Ms Hellman's body was called off Mr Bennett asked the Coast Guard for a "letter of presumed death", the Palm Beach Post reported.

Bennett is scheduled to attend a bail hearing in the US District Court in Key West, Florida, on Friday.

AAP