Due to his mysterious disappearance, a phrase has entered into Australian slang: "Time to do the Harold Holt", popularised by a television commercial for Red Bull, means "to disappear". (Arguably, the way that the advert uses the term could make it rhyming slang for "bolt", as in "run".) The advert consists of a swagman, obviously a fugitive, hearing distant sirens (uttering the erstwhile phrase as he does) and drinking some Red Bull, leaving it at the scene. When the police arrive, they find the empty can and give up in disgust.
Holt's body still hasn't been found. In 2003 (two years after the above writeup) there was finally a coroner's inquest into his death, but nothing changed and no new evidence was given: the finding, drowning in accidental circumstances. Conspiracy theories still abound, from committing suicide to being a Chinese spy, to the CIA having him killed. However, the most likely scenario is that he just drowned, as he had a heart condition and a bad shoulder that likely caused him problems while swimming. In addition, Cheviot Beach is known for its dangerous currents and sharks; it is likely that sharks consumed his carcass.