The boater whose wife vanished in the Bahamas will remain in police custody after investigators were granted a 72-hour detention extension.

Brian Hooker, 59, was arrested by the Royal Bahamas Police Force on Wednesday - after his wife Lynette, 55, allegedly fell overboard into the waters off the Abaco Islands.

Under Bahamian law, authorities have four days to decide whether or not to charge him with a crime before they must release him.

But investigators were granted a special 72-hour extension that will keep Hooker jailed until around 7.30pm tomorrow, his attorney Terrel Butler said.

The extension came after the lawyer revealed that Hooker requires medical attention after he fell overboard from a police transit.

'He was submerged in the cold water and took in a significant amount of seawater before his life jacket brought him to the surface. He had to be rescued from the water by the police,' Butler told the Daily Mail.

'As a result of this fall, Brian sustained an injury to his knee, which has caused him to limp, as well as a visible abrasion.'

Hooker - who has not been charged and denies any wrongdoing in Lynette's disappearance - is being questioned in relation to the Bahamian crime 'causing harm resulting in death.' 

Under the extension, the deadline for Hooker's release is now Monday night - though he could be released before then if police decide not to charge him.

'This extension was granted under Section 19 of the Criminal Procedure Code, of the Bahamas, which allows a Magistrate to authorize further detention for up to 72 hours where an investigation is incomplete,' Butler revealed Friday.

She reiterated his innocence and said his wife has not been found. 

Butler said police had just finished an intensive four-hour interview with him in which she described him as continuously asking about his wife.

'He was a bit puzzled because he was uncertain as to why they were questioning him about causing harm or possible murder when they had not given him any information in terms of where she is, if they had recovered her,' she said.

Hooker was detained on the Abaco islands four days after he returned from the expedition without her, claiming she fell overboard.

Authorities first interviewed Brian and released him, then brought him back in as a witness for further questioning.

He was later brought in for questioning a third time, as a suspect, according to Butler.

Hooker himself fell after being arrested on Wednesday night, his attorney told the Daily Mail.

'Under conditions of heavy rain and strong-force winds, he was taken by boat to his boat, the Soulmate for a police search,' she said. 'Despite the choppy and dangerous sea conditions, he was kept in handcuffs.

'While attempting to move sideways across the wet, unstable flooring of the boat to maintain his balance—with a bundle of clothes in his restricted hands—he lost his footing and fell overboard.'

He sustained an injury to his knee, and instructed Butler to request 'immediate medical attention' on his behalf.

He is understood to have been transported to Rand Memorial Hospital for treatment and a full medical assessment.

Butler, who said she is monitoring his condition, added that her client appears 'completely heartbroken' and 'deeply distressed' by Lynette's disappearance.

'His primary concern and source of intense frustration is his inability to continue the search for his wife of 25 years,' she said.

'The trauma of her disappearance, coupled with his current detention as a suspect, has left him in an extremely fragile state.'

Hooker told police that Lynette fell overboard Saturday night from a small dinghy that was carrying the couple from Hope Town to Elbow Cay, small islands on the eastern end of the Bahamas. 

He had been alone in the eight-foot vessel after Lynette plunged over the side around 7.30pm, taking with her the engine's kill-switch key which was attached to her by a cord. That cut the tiny vessel's power.

Hooker staggered ashore hours later and admitted that he and Lynette had been 'drinking' and 'were drunk,' boatyard security guard Edward Smith told the Daily Mail.

Smith said Hooker showed little visible emotion as he shared how Lynette had been 'thrown' from their small dinghy in darkness and rough seas as they headed back to their moored vessel in the Abaco Islands. 

He said the couple had been returning to their 50-foot sailboat, Soulmate, from Elbow Cay when, 'my wife was just thrown out of the boat' in atrocious weather, the watchman recalled.

'He wasn't crying or anything. He didn't seem stressed in that way. There wasn't a lot of emotion. There were no tears,' Smith told the Daily Mail.

'He expressed nothing that you would imagine in those circumstances. He was more exhausted than emotional because he kept asking for water.

'He drank and kept asking for more. He had some water from my cooler, I then gave him another liter. He drank that down and then he wanted even more.'

Hooker ditched the dinghy just south of the boat yard where Smith works in Marsh Harbour on the main Great Abaco Island around 4am Sunday and stumbled along rocks until he found rescuers.

According to his account to the security guard, Hooker battled more than eight hours and with just one paddle to cover around seven miles to shore on the main island after 'losing sight of my wife'.

Authorities say they are in a recovery operation to find Lynette's body, but there has still been no sign of her. 

The US Coast Guard's high-tech imaging aircraft has scanned the entire area in a systematic grid without any results, the Daily Mail has learned. 

Smith believes sharks will have pounced within minutes – a belief backed up by a highly experienced high-end boat skipper who also spoke with the Daily Mail.

Bahamian authorities have released few details about the case, but say the investigation into Lynette's disappearance remains ongoing. 

The US Coast Guard has also opened an investigation that is separate from the one by Bahamas authorities. 

In a statement to the Daily Mail, Hooker said he is 'heartbroken' by his wife's disappearance, describing the incident as a 'boat accident in unpredictable seas and high winds.' 

'Despite desperate attempts to reach her, the winds and currents drove us further apart,' he said. 'We continue to search for her and that is my sole focus.'

Lynette's distraught daughter Karli Aylesworth has said it's unlikely her mother would 'just fall' from a boat.

And while the couple is seen smiling, laughing and joking in social media videos of their voyage, they have a history of contention.

Brian and Lynette Hooker accused each other of assault in 2015, according to a Kentwood, Michigan police report.

Brian Hooker, who was intoxicated and bleeding from the nose, told police his wife had struck him multiple times in the face, the report said. 

He told officers Lynette also was drunk. She was arrested for assault and spent the night in jail. A warrant was denied because it wasn't clear 'who started the assault.'

In an interview with Fox News, Aylesworth referenced 'prior issues' in Lynette and Brian's marriage and claimed they had a 'history of not getting along, especially when they drink.'

'There is a history of him choking her out and threatening to throw her overboard. So, the fact that this is actually happening makes me believe there's more to the story,' she told the outlet.

'There has also been a history of domestic violence in that relationship, so I do believe something might have happened to her.'

Aylesworth has not responded to the Daily Mail's multiple requests for comment. 

Butler said, in a statement, that Brian's denial of wrongdoing includes in particular 'the allegations recently made by Karli Aylesworth.'