MIAMI — A shifty sailor whose newlywed wife mysteriously went missing at sea as they cruised around the Caribbean for their honeymoon, has finally acknowledged that he killed her.

Lewis Bennett, 41,  a mining engineer with dual British and Australian citizenship, had long insisted he left his wife, Isabella Hellman, on deck in May 2017 when he went to their cabin to go to sleep. He said he later awoke when the boat hit something and that Hellman was gone.

But he has now pleaded guilty to involuntary manslaughter, with federal prosecutors asking for a sentence of eight years when he is sentenced in January. In his plea agreement, Bennett described his wife’s death as an accident that he did not witness, while admitting it was his fault, the Florida Sun-Sentinel reported.

Hellmann disappeared from the couple’s 37-foot catamaran, Surf Into Summer, as the couple sailed near the Bahamas on their way to Florida.

Bennett told investigators at the time that the boat experienced difficulties while he was sleeping below deck and Hellmann was on watch. He said she was missing when he came above deck after a loud noise woke him up.

After realizing the vessel was sinking, he said he gathered his belongings and abandoned ship.

He sent out an emergency alert about 30 miles from Cay Sal Bank in the Bahamas. He also made a phone call and reported that he was in distress on a life raft.

Hellmann’s body was never found and she is presumed dead. She was 41.

In court, Bennett admitted he did not require his wife — a weak swimmer and inexperienced sailor — to wear a life vest or harnesses tethered to their catamaran, all of which were on the vessel.

Bennett, who is a strong swimmer and has extensive training and experience in sailing, also acknowledged he did almost nothing to try to find his wife.

“Mr. Bennett could not recall whether he called out her name. Although Mr. Bennett threw a horseshoe life ring overboard, he did not deploy flares to illuminate the area to look for his wife or to signal his position, nor did he turn the catamaran around to look for her,” according to the plea agreement. “Additionally, Mr. Bennett did not search for her with the catamaran or the dinghy that was attached.”

But he did spend maybe 45 minutes loading up a life raft with food, water, safety devices, a satellite phone – and about $40,000 worth of stolen silver and gold coins.

Prosecutors said there was evidence that the damage inflicted on the catamaran appeared to be intentional, not accidental.

The couple, who had an infant daughter, had been married for only a few months but their marriage was already crumbing under heavy financial duress, prosecutors have said.

Prosecutors said that Bennett had a motive to kill his wife, a real estate broker who was born in Colombia but became a U.S. citizen after moving to the U.S.

“[Bennett] and Hellman were undergoing intense marital strife that was causing their marriage to deteriorate. That marital strife concerned disagreements about finances, arguments over a variety of topics, and the defendant’s treatment of Hellman,” prosecutors wrote in court filings.

“[His motive] was to remove the marital strife between them, enable him to inherit her estate, obtain complete control over the finances, and allow him to live his life as he pleased without any input from Hellman.”