Isabella Hellmann, 41, vanished when the couple’s catamaran sank in the straits of Florida in May 2017.
Her husband, Lewis Bennett, 42, was found in a life raft with antique coins which he had previously reported as stolen.
He apologised to the family of Isabella Hellman during a Tuesday hearing before District Judge Federico Moreno in Miami.
Bennett’s legal team sought a seven-year sentence but the judge went with the maximum number of years spelled out in a plea agreement on an involuntary manslaughter charge reached last November.
Bennett was originally charged with murder, with investigators alleging he intentionally tried to sink the boat, but later dropped the charges.
“It’s not because I expect that he will commit this crime again,” Judge Moreno said. “Sentencing is for punishment.”
Bennett, a dual Australia-UK citizen, had asked the judge to let him out of prison sooner so he could raise the couple’s daughter, who turns three in July and is being raised by Bennett’s parents in Scotland.
“If you may permit me to be with my daughter as soon as possible,” Bennett said. “I want to bring her up in a manner that is respectful to my wife’s wishes.” But Moreno sided with prosecutors and chose eight years in prison as the sentence and three years on supervised release.
Ms Hellman disappeared as the couple sailed off the Bahamas in May 2017.
A statement from the US Attorney’s office says Bennett had experience sailing, including training on emergency procedures, and had previously travelled from St Marteen to Australia.
His wife, a naturalised US citizen born in Cuba, had not trained in emergency sailing procedures and had less experience.
The couple had been married for three months when they set sail to St Marteen, Puerto Rico and Cuba for a delayed honeymoon in late April.
After they left Cuba on May 14, Bennett asked Ms Hellman to take over control of the boat for the night so he could go rest in the boat’s cabin, according to court documents.
He didn’t require her to wear a life jacket, harness or personal locator, prosecutors said in the statement.
He said he woke up when the craft hit something and Ms Hellman was missing. The government maintained he didn’t use the satellite phone to call for help. Instead, he loaded provisions and stolen silver coins onto a life raft and boarded it.
Prosecutors said he called for help 45 minutes after he had woken up realising his wife was gone.
A US Coast Guard helicopter rescued him; authorities searched for Hellman for four days, but never found her body.
A Florida state judge declared Ms Hellman dead earlier this month to clear the way for the couple’s daughter to inherit her mother’s estate.
“Hellman’s death occurred as a result of Bennett’s knowledge of circumstances that existed that could have reasonably enabled him to foresee threat to life,” the US Attorney’s office said in a statement Tuesday.
The FBI said an inspection found that holes in the hull were inflicted from the inside and hatches were opened in a deliberate attempt to sink the boat. Bennett was initially arrested and charged with murder last year before reaching a plea deal with federal prosecutors. He had already pleaded guilty to transporting $US100,000 ($A144,340) in stolen coins.
— with AP