Later on this month they will gather to remember their loved ones at a memorial service marking the 25th anniversary of her sinking.
The names of the dead including Francesca Dallaglio, 19, sister of former England rugby captain Lawrence Dallaglio, and Antonio de Vasconcellos, whose 26th birthday was being celebrated, will be read out on August 20 by Southwark Cathedral Dean the Very Rev Andrew Nunn. Two launches will later take families out to the spot to lay flowers.
On a hot late summer evening on August 20 1989, the pleasureboat Marchioness packed with partygoers, collided with the dredger Bowbelle on the Thames, in central London.
Two inquiries 10 years apart found that the failure of both vessels to keep a proper look-out was the immediate cause of the tragedy.
Margaret Lockwood Croft, now 74 and a great-grandmother three times over, lost her son Shaun, 26, in the disaster.
She says her work as the director of the safety-seeking body the Marchioness Action Group “has kept me going”.
Mrs Lockwood Croft, from Aldershot in Hampshire, said: “It still feels like yesterday it happened. It’s all still so vivid.
“First there was this sense of numbing disbelief, then physical pain and then anger. For me, it was a question of flight or fight. I could have taken flight but I decided to fight. I was not going to allow what had happened to destroy me.”
Thanks to the efforts of Mrs Lockwood Croft and others bereaved by the tragedy in 1989, safety regulations on the Thames have been tightened.
Following Lord Justice Clarke’s 2001 report, which found it was a “catastrophe that should never have happened” the first lifeboat services were introduced on the Thames in 2002.
There are now four, with one based close to the Tower of London, one of the busiest in the country.
But Mrs Lockwood Croft believes people should have to take the equivalent of a driving test before embarking on inland waters. “They should have to pass a basic test”, she said.