Hint: The cause of death was not radiation poisoning contracted from swimming in the Mediterranean.
The answer is after the JUMP.
Two years later, Lyndon Johnson appointed him ambassador to Spain. When the United States accidentally dropped unarmed hydrogen bombs off the Spanish coast, he went for a swim in those waters to publicly demonstrate that there was no danger of radiation poisoning.
In the spring of 1995, he died in a rollerblading accident near his Southampton, Long Island home. It was a tragedy to be sure, but all things considered, a rather glorious way for a man of his advanced age to meet his end. Should we all remain so athletic.