He is thought to have gone overboard early in the morning but was not reported missing until about 1100 local time (1000 GMT) when he failed to answer a telephone call.
Two helicopters, rescue launches and a dozen ships were then sent to the area to assist in the search. It was not immediately known how Mr Maxwell ended up overboard. The Prime Minister, John Major, led the tributes to Mr Maxwell, calling him a "great character".
From humble beginnings in Czechoslovakia, Robert Maxwell became one of Britain's richest men. He enlisted in the British army during World War II and was decorated for bravery. He subsequently worked for the Foreign Office before building his business empire.
In 1984 he achieved a long-held ambition to own a national newspaper when he bought the Daily Mirror. Earlier that year Mr Maxwell also purchased a New York paper, the Daily News, which had been on the brink of closure. But at the same time he was being forced to sell off companies to reduce his debts, prompting criticism of his business methods and abrasive management-style.
Dealing in shares in Mr Maxwell's Mirror Group was suspended after the news of his disappearance became public. Mr Maxwell's sons, Kevin and Ian, were put in charge of his business.
After Robert Maxwell's death it emerged that the Mirror Group's debts vastly outweighed its assets and £44om was missing from the company's pension funds.
In 1996, after an eight month trial, Kevin and Ian Maxwell and another man, Larry Trachtenberg, were cleared of conspiracy to defraud Mirror Group pensioners.
In 2001 the Department of Trade and Industry released a report into the Maxwell affair which said "primary responsibility" for the collapse of the Maxwell business empire lay with its founder.