Mrs Hick, from Shannon in the Manawatu, was the driving force behind the plaque, on the Wahine mast at Frank Kitts Park onthe central Wellington harbour front.
She told a crowd of about 200 she lost "a beautiful angel" to the disaster. Her son Gordon died young as the result of brain damage suffered as a baby when the ferry sank.
"We will never forget the people who rescued us," Mrs Hick told the crowd, many of them survivors and rescuers.
"From the survivors, thank you." Fundraising for the the plaque wasn't east and Mrs Hick had a dig at Wellington businesses for their lack of support.
After the unveiling there was a private wreath-laying and prayer by Dean Frank Nelson at the Museum of Wellington.
An updated list of those who died in the disaster was then unveiled.
In contrast to the hellish 1968 storm which sank the Wahine in Wellington harbour, the commemorations took place on a cloudless autumn day and a light breeze.
The Wahine sinking claimed 51 lives on April 10, 1968, with two others dying later as a result of injuries sustained on that day.
Those two names were added to a list of casualties devised by the Museum of Wellington, which organised the commemorations.
May Elizabeth Brightwell was added to the list today, nearly 40 years after the coroner ruled she died of injuries received in the sinking.
Gordon Hick was added 18 years ago, when he died young as the result of brain damage as a baby when the ferry sank.
Other events include a private wreath-laying ceremony, an unveiling of the updated list of those who lost their lives and a visit to the Wahine memorial on Miramar peninsula, in view of where the ship sank.
