Welder Finlay McGregor praised his rescuers
A passenger on the helicopter that came down over the North Sea said he felt an impact moments before it hit the water.
Finlay McGregor, from Tain, in Ross-shire, said: "It was if something had fallen off, or we'd hit something. It felt like being rear ended by a truck."
The welder was among 18 people on board the Super Puma that came down 125 miles east of Aberdeen on Wednesday evening. All were rescued.
The Air Accidents Investigation Branch (AAIB) is probing the ditching.
Mr McGregor, 56, said the impact was felt as the helicopter made its final approach to a platform in the Etap field.
He told BBC Scotland: "The next thing I knew we were in the water and going through the evacuation process.
"We got the helicopter doors open and everybody was quite calm and helping each other, although we were scared out of our wits.
"We'd been knee deep in water inside the helicopter.
"Happily the helicopter stayed afloat and I was glad to get into a life raft and was glad that the sea was calm."
Mr McGregor said the lights from helicopters looking for them could be seen through fog.
Distress flares were fired from the life rafts to help guide rescuers to their position.
The welder added: "We were really, really cold and a few were being sea sick. We waited around an hour for rescue - but it seemed a lot longer."
He also thanked the crew of the vessel Caledonian Victory which picked up 15 of the men and took them to Aberdeen.