The various US governments during Fidel Castro reign tried to kill him over 600 times. Fabian Escalante, the former head of the Cuban Secret Service, estimates that the assassination attempts break down like this: the Eisenhower administration tried to kill Castro 38 times; Kennedy, 42; Johnson, 72; Nixon, 184; Carter, 64; Reagan, 197; Bush Sr., 16; Clinton, 21.(the exact numbers are disputed).
The CIA tried various (sometimes stupid) methods to assassinate the Cuban leader. When wild unorthodox methods like cigars(poisoned and exploding), contaminated air, poisoned pills, fungus and a poison-filled syringe failed, they came out with even wilder schemes like placing thallium salt in his shoes, in the hope that his beard would fall out(seriously ‘Murica?!).
Then someone at the CIA came up with a crazy plan to kill him using a Seashell.. Yeah a goddamn booby-trapped SEASHELL! You see, the dictator was a fan of skin diving, so intelligence agents plotted to place an especially spectacular shell in a reef Castro was known to frequent. The hope was that the shell would be so beautiful that Castro would pick it up and, by doing so, trigger an explosive.
Unfortunately (or fortunately for the Cubans), this elaborate, vacuous plan was later deemed unpractical and was dropped.