''I wrote it for my sons, to show them never give up, never stop kicking, just keep going.''
Mr Reedy, of Invercargill, was rescued after 18 hours of clinging to an empty plastic petrol container.
He was a deck hand for his friend of 20 years, skipper Rewai Karetai, who drowned along with the other seven people on board.
Mr Reedy was at the Invercargill District Court yesterday to support Mr Karetai's widow, Gloria Davis, as she and her company were sentenced on charges relating to the sinking.
Afterwards, Mr Reedy said the sentencing meant everyone could get on with their lives again, and he could push on with plans for his book.
''I waited till after all this was over, just out of respect for Gloria.''
He had completed a draft and was negotiating the book's release with several publishing companies.
Davis had read the draft, he said.
Asked what her reaction had been, he said ''she kept her copy'' and was fine with him writing it.
The families of the others who drowned also knew about the book and were supportive.
During Davis' trial in January, Mr Reedy gave harrowing evidence about the moment at 12.03am on March 15, 2012, when a huge wall of ''black water as far as the eye could see'' swamped Easy Rider, flipping it in seconds.
He heard the youngest passenger, Odin Karetai (7), who had been in the wheelhouse asleep on his father's knee, screaming.
Then the scream was cut off.
Mr Reedy was washed into the sea and did not see or hear any of the others after that.
Mr Reedy said yesterday one of his reasons for writing the book was to show that his friend Rewai ''Spud'' Karetai - Rewai is Maori for potato - was not as incompetent as he had been portrayed at the trial.
Mr Reedy had worked with him on boats on and off for years and said at the trial he considered Mr Karetai a ''first-class fisherman''.
''It's a good thing I survived. Now, I can tell it like it was and tell people what Spud was really like.''