A British man has been arrested on suspicion of murdering his wife, who he reported missing as they sailed off the coast of Cuba last year, the FBI has announced.

Lewis Bennett, 41, of Poole, Dorset, was arrested while he was waiting to be sentenced at a court in Miami for smuggling stolen coins during the voyage in May from which he was rescued alone.

The gold and silver coins were allegedly from a batch worth up to $100,000 (£75,000) that Bennett reported as stolen from his employer a year before his rescue.

The FBI brought the new charge as it investigated the disappearance of Isabella Hellman. In a court document, FBI special agent James Kelley said the bureau believed Bennett “knowingly and unlawfully killed” Hellmann.

The newlyweds had been sailing home from Havana to Florida when Bennett, who has dual Australian citizenship, made an SOS call in the early hours of 15 May.

He described how he had been awoken by a large thud, having last seen his wife the evening before when he left her in charge of the 11 metre (37ft) catamaran.

He said when he went on deck, his wife had disappeared. After realising the boat was taking on water, he fired his emergency positioning beacon and sent out a distress signal.

Two hours later, Bennett was rescued from his life raft by a US Coast Guard helicopter. A four-day air and sea search for Hellman was unsuccessful.

The coast guard diver said the yachtsman only took one “unusually heavy” backpack with him from the raft, the court heard. The bag was never searched, but among Bennett’s belongings left on the raft were nine plastic tubes holding the silver coins.

About a week later the coins were returned to Bennett at his home in Delray Beach, Florida. Later that day the FBI realised Bennett had reported that the coins had been burgled along with others from an employer’s boat in St Maarten a year earlier.

Investigators returned to search Bennett’s home and found a further 162 gold coins hidden in a pair of boat shoes in a closet, according to court documents.

In December, Bennett pleaded guilty to the charges of theft and attempted smuggling, which would have carried a maximum of 10 years in prison.

Bennett’s family last month wrote a letter to the judge in the case, asking him to be lenient with the sentence owing to his young daughter already having lost her mother.