Honouring the man still revered as the moral conscience of the nation, Gandhi's followers had carried his ashes through the streets of Mumbai to the coast, where the procession was met by a platoon of police and assembled local politicians.
The small copper urn, wreathed in garlands of white flowers, was then taken out to sea on a speedboat, pursued by a flotilla of cameramen and reporters.
Nilamben Parikh then poured the contents into the sea, completing a ritual that finally laid India's secular saint to rest and marked the healing of a generations-old rift among his descendants.
The urn was one of dozens containing Gandhi's cremated remains that were distributed around India after he was shot dead by a Hindu extremist on January 30 1948 at a prayer meeting in New Delhi. The distribution denied Gandhi the traditional Hindu burial he had wanted but placated the mourning masses of newly independent India.
The ashes spread at sea today had been intended for display at Mumbai's Mani Bhavan Gandhi museum, having been bequeathed by an Indian businessman in Dubai whose father had been a close friend of Gandhi.
But Gandhi's family objected to the apparent deification of a relic, saying it could be misused for politicians in search of votes. Instead, the relatives wanted to scatter the ashes at sea, a ceremony also intended to symbolise the healing of a rift between Gandhi and his estranged eldest son, Harilal.
Parikh, an author, is the granddaughter of Harilal, who flirted with Islam but died virtually unnoticed as a penniless alcoholic, having outlived his illustrious father by only a few months.
Flouting Hindu tradition, Harilal did not perform the last rites at the burning pyre of his father, instead letting his two younger brothers take his place. The rancour had started after Gandhi, then fighting colonial rule in South Africa, refused to bend the rules to get Harilal a scholarship so he could go to London to become a barrister.
A film, Gandhi, My Father, released last year, explored the troubled relationship, portraying the leader, whose credo of non-violence ended the British Raj, as an unforgiving patriarch whose ideals shaped a nation often at the expense of his family.
In pouring the recently rediscovered ashes into the warm waters off Mumbai's Chowpatty beach, Parikh said she had "closed a chapter".
Gandhi's great-grandson, Tushar Gandhi, said: "It is important that all members of the family are here. We are all very close and the decision was taken by everyone for Harilal's children to immerse the ashes.
"The emotional aspect of this is that duties that Harilal should have performed have been completed by his descendants. It is of symbolic importance for us."
In 1997, Tushar poured what were then believed to be the last ashes of Gandhi into the meeting place of two of Hinduism's holy rivers, the Ganges and Yamuna. He had found his ancestor's remains in a bank vault in India and gone to the courts to secure them for the family.
Many other urns are thought to remain in the hands of devotees, including one that is enshrined in an ashram in California and another installed in the palace of the Aga Khan, the head of the Islamic Ismaeli sect, in southern India.
"I have no doubt there are other urns floating around but the family has taken the view that the Mahatma asked for his ashes to be scattered as per Hindu customs. That is what we are trying to do," said Tushar.
Although Gandhi is still revered - his face can be found on rupee notes and on hoardings exhorting people to do the right thing - the scattering did not attract huge crowds. A few hundred turned up to listen to the speeches and religious songs being played.
Some experts say that Gandhi's ideas are irrelevant in modern India.
"India today has repudiated everything he stood for," said Rudrangshu Mukherjee, editor of the Penguin Gandhi Reader.
"He did not want industrialisation, he did not want a strong centralised state, he did not want violence or religious intolerance. Yet this is India today. He is at best an icon, respected but not relevant."
© Guardian News and Media Limited 2008