On 17 December 1967, Harold Holt, the Prime Minister of Australia, disappeared while swimming in the sea near Portsea, Victoria. An enormous search operation was mounted in and around Cheviot Beach, but his body was never recovered. Holt was presumed to have died, and his memorial service five days later was attended by many world leaders. It is generally agreed that his disappearance was a simple case of an accidental drowning, but a number of conspiracy theories surfaced, most famously the suggestion that he had been collected by a Chinese submarine. Holt was the third Australian prime minister to die in office, after Joseph Lyons in 1939 and John Curtin in 1945. He was initially replaced in a caretaker capacity by John McEwen, and then by John Gorton following a Liberal Party leadership