The US hatched strange and spectacular plots to kill Fidel Castro, according to never before seen files.

The JFK files – many of the most important of which appear to have been held back – have not provided a smoking gun in the killing of the president, or shed more light on how that assassination was able to happen. But they do show the US's plans for another high-profile killing: its plot to kill Fidel Castro.

It has long been known that the company hatched elaborate schemes to kill the Cuban leader. But the documents show just how strange and detailed those were – including plots to kill him off with a festering swimsuit, and the idea of creating a deadly, boobytrapped shell that would catch his attention.

The assassination of JFK – in pictures Show all 8 1 /8 The assassination of JFK – in pictures The assassination of JFK – in pictures President John F. Kennedy and his wife Jacqueline Kennedy ride with secret agents in an open car motorcade shortly before the assassination, 22 November 1963 Getty The assassination of JFK – in pictures President John F. Kennedy and his wife Jacqueline Kennedy prior to his assassination Keystone/Getty The assassination of JFK – in pictures Kennedy is struck by an assassin's bullet as he travels through Dallas in a motorcade In the car next to him is his wife Jacqueline and in the front seat is Texas governor John Connally Three Lions/Hulton Archive/Getty The assassination of JFK – in pictures The view from the sixth floor window of the Texas School Book Depository in Dallas, from which Lee Harvey Oswald is thought to have assassinated Kennedy. This photograph was taken approximately one hour after the assassination Hulton Archive/Getty The assassination of JFK – in pictures Lee Harvey Oswald during a press conference after his arrest in Dallas. Lee Harvey Oswald was killed by Jack Ruby on 24 November on the eve of Kennedy's burial AFP/Getty The assassination of JFK – in pictures Lyndon B. Johnson takes the oath of office as President of the United States on the day of Kennedy's assassination. Jackie Kennedy is stood next to Johnson Getty The assassination of JFK – in pictures Kennedy's funeral procession goes into Arlington Cemetery in Washington Newsmakers/Getty The assassination of JFK – in pictures Kennedy's casket sat in the East Room of the White House Newsmakers/Getty

The first saw the CIA attempt to convince an American lawyer who had been negotiating with Castro to give him a gift that would kill him. That was to be a special diving suit that would be infested with deadly bacteria, killing the leader once he put it on.

"It was known that Fidel Castro liked to skindive," the paper reads. "The CIA plan was to dust the inside of the suit with a fungus producing madera foot, a disabling and chronic skin disease, and also contaminating the suit with tuberculosis bacilli in the breathing apparatus."

But Donovan didn't take up the US on the plan. Instead, he did exactly the opposite, giving Castro “an uncontaminated skindiving suit as a gesture of friendship.”

Another plot saw spies discuss the possibility of planting a "spectacular seashell" that would catch Castro's attention. But once he swam towards it, the explosives inside would be set off and kill him, they suggested, but that plan was also abandoned.

"After investigation, it was determined that there was no shell in the Caribbean area large enough to hold a sufficient amount of explosive which was spectacular enough to attract the attention of Castro," one of the documents reads.

Though Cuba hangs over much of the US's response to JFK's assassination, the conclusion appears to be that the Cuban government wouldn't have been the ones to have the president killed. A draft report from the House Select Committee on Assassinations suggests that the risk would just have been too high.