"Unfortunately, when Mr Preston put his on, it wasn't completely fastened. He was unable to hold on to it and would have slipped out of it."
The group had planned to go fishing in Kawau Bay, and set off from Martins Bay, near Warkworth, on Tuesday.
About 3pm, the engine of their 6m aluminium runabout stopped and the boat started to fill with water. It capsized, and they ended up in the water.
The men were separated and the last time Mr Preston was seen was just after dark.
His lifejacket was found floating on the water the next day, but searchers have not been able to find him.
His fishing mates swam about 2km to nearby islands, where they spent a cold night in temperatures of less than 5C.
Two of the men and the 13-year-old reached Motuketekete Island. The other man landed on a small island next to Motuketekete.
"He ended up by himself. He thought he was the only survivor," said Mr Paget.
"They were on two small islands joined by a reef that you can walk across when the tide is low. The next morning, the single person started walking to see how he was going to get off the island and saw the others on the adjacent beach."
The group then had to wait until the tide went out to reunite.
They were found together just before 10am on Wednesday, after they were reported missing by the wife of one of the men.
They were not reported missing earlier as they had not left firm details about their plans.
Two of the survivors remained in North Shore Hospital last night.
It had been hoped they would be discharged yesterday, but their conditions were worse than doctors initially thought.
The third man was discharged on Wednesday, and the 13-year-old boy was to be given the all-clear to return home last night.
Mr Paget said police hoped to keep searching until Mr Preston was found.
