The first man on the scene of the accident was Nigel Locke, who was visiting his sister in Weymouth.

Mr Locke, 57, pictured, of Clanfied, Hampshire, said: “I was standing above the pontoon with my girlfriend Jan. We were waiting for the speed-boat ride.

“I saw Mark go down the steps and then I just saw an arm go up and thought, ‘he’s gone in’.

“I was half way down the steps when Mark came up the second time and he just let out this scream.

“I will never, ever forget it – it was so sincere and desperate. It was horrendous and will stay with me.”

Mr Locke paid tribute to the coastguards and ambulance crew and the three other unknown rescuers who helped to pull Mr Scales out.

He said: “They were fantastic.

“I’m no hero, it was a team effort.

“I was just the first guy there and I’m so happy and glad that Mark is ok and that I could help. I feel so sorry for him, it must have been horrific for him being and disorientated under the pontoon.”