Missing mom's husband sought 'presumed death' letter days after Bahamas disappearance

The newlywed husband of a mother who vanished while the couple was sailing in the Bahamas had asked the Coast Guard for a "letter of presumed death" a day after the agency called off their search, and within four days of their boat overturning, according to court documents.

Isabella Hellmann's sister has accused her husband Lewis Bennett of killing her, according to a police report issued after her disappearance. Bennett has not been formally named as a suspect in her disappearance.

Authorities have also never said that they suspect the disappearance of the 41-year-old mother was the result of foul play, and the investigation into her disappearance is still being treated as a missing persons case by the Coast Guard and the FBI.

A May 19 letter from the Coast Guard to Lewis Bennett, Hellmann's husband of just three months and father of their 9-month-old daughter, informed him that it isn't authorized to issue a letter of presumed death. The letter is included in documents related to an action Hellmann's sister, Adriana Difeo, filed in the Palm Beach County court in June in an effort to take over Hellmann's finances.

The Delray Beach, Florida couple was celebrating their marriage by sailing the Caribbean. The boat was reported capsized on May 15 near the Bahamas, and the search for Hellmann was called off on May 18.

Bennett told the Coast Guard that Hellmann had agreed to take watch above deck. He awoke to the sensation of something hitting the boat, he told the Coast Guard, and the feeling that the vessel was starting to sink.

Bennett also told the Coast Guard that when he couldn't find Hellmann he jumped onto a life raft and sent out a distress call. He was found on the life raft on May 15, according to the Coast Guard.

Florida law states that a person can't be declared legally dead until he or she has been missing for at least five years.

Areva Martin, a legal analyst, told ABC News that Bennett's request from the Coast Guard doesn't add up, given the details spelled out by Florida's missing person law.

"There's not a clear indication as to why he would want this letter, particularly in light of Florida law, which says a person is not presumed dead that goes missing until after 5 years has elapsed," Martin said.

The letter from the Coast Guard notes that "a combined 137.77 hours spanning 4,980 square nautical miles with four types of aircrafts and three CG cutters" was dedicated to their search for Bennett, but they were unable to find her.

Friends of Hellmann have told ABC News that the couple had gotten into a fight about the possibility of moving to Bennett's native Australia.

"She was set on, 'no, I'm not moving,' and he was upset [about] her not wanting to go with him," Sarah Cortes, a friend of Hellmann's, told ABC News. "The family is destroyed, the family is extremely hurt."

ABC News Ben Stein contributed to this report.