A newlywed British-Australian sailor whose wife died after their yacht sank off the coast of Cuba during a honeymoon trip has been jailed for eight years in the US for her manslaughter.

Lewis Bennett was sentenced on Tuesday at a Miami court for the killing of Isabella Hellmann, 41.

Bennett, 42, of Poole, Dorset, was initially accused of murder and intentionally scuttling the catamaran before he pleaded guilty to the lesser charge of involuntary manslaughter.

He must also pay $22,910 (£18,130) in restitution and will spend three years on supervised release after serving his sentence, a spokeswoman for the US justice department said.

Isabella Hellmann, 41, vanished when the couple’s catamaran sank in the straits of Florida in May 2017. Photograph: Facebook

Bennett apologised to Hellmann’s family during the hearing before the US district judge Federico Moreno, who rejected his defence lawyer’s request for a seven-year sentence.

The couple had been married for three months when they set sail to St Maarten, Puerto Rico and Cuba for a delayed honeymoon in late April. The couple, who had recently had a baby daughter, had been sailing from Cuba to their home in Delray Beach, Florida, when Bennett sent a distress signal on 15 May 2017.

The experienced sailor, with dual British-Australian citizenship, claimed he woke to find his novice passenger missing from the 34ft vessel, Surf Into Summer, but he only reported her missing 45 minutes later, after he had fled in a liferaft carrying Cuban trinkets, a tea set and a jar of peanut butter.

The catamaran belonging to Lewis Bennett. Photograph: The United States Department of Justice/PA

He was found to be smuggling rare coins worth nearly $30,000, which prosecutors cited as another potential reason he may have wanted his wife dead. He had reported the gold and silver collectables stolen from a former employer in St Maarten a year earlier.

He was plucked from the sea but, despite an extensive search, his wife’s body was never found and she was declared dead by a judge earlier this month.

Bennett was already serving a seven-month jail term after admitting transporting the coins.

Prosecutors had alleged he murdered Hellmann and deliberately sunk the catamaran to end his “marital strife” and inherit her home and wealth, but they reduced the charge to unlawful killing without malice and Bennett pleaded guilty.

Press Association and Associated Press contributed to this report