Of the many CIA-devised plans to assassinate Cuban dictator Fidel Castro in the late 1950's and early '60's, the "Booby-trapped Sea Shell" plot was by far the most bizarre and amusing. The idea was to rig an attractive-looking sea shell with explosives so that when it was lifted it would explode. US agents would then place the armed shell on the shallow ocean floor near the beach where Castro frequently swam. Unable to resist the shell's natural beauty, the CIA presumed that the dictator would try to recover it from the ocean, thus detonating the device.
Of course, the CIA quickly found the half-baked plan to be impracticable and it was abandoned due to size restraints (the shell was too small to load with sufficient explosive) and transplantation issues (the submarine proposed to plant the shell had too short of a range). While the planning took place during the Kennedy administration, it is unconfirmed how many people were told of the idea.