Mr O'Connor jumped about 6m into the dark, cold water, landing on his back.
"I never expected the cold, it didn't enter my head when I jumped in. It certainty did when I hit the water though."
He swam up to Mr Donkersley, who at that point was unresponsive. He put him onto his back into the rescue position.
"I didn't know if he was alive or dead for the first few minutes," Mr O'Connor said.
Mr Donkersley began responding after about 15 minutes.
"We just cracked jokes and I tried to make him calm. I had to keep our spirits up, I knew once the cold got us that we weren't going to survive very long there."
They spent 40 minutes in the cold, winter water before coming ashore.
"I look out there and think, when it's nice and calm and smooth, anybody could do it. But when I go through there on a stormy day I think, how the hell did I manage to get out of that one. I think both Ash and I had someone looking out for us that night, and we were just very, very lucky."
"I'll never forget. Ever. It just never goes away."
"I can't drive over that bridge without slowing right down, it just freaks me out."
"It's just something you reflect back on... that I did save a young guy's life and that's quite a humbling experience, it's quite amazing to know that you've managed to bring this person back and also the fact that he's gone on to have a child as well."
Mr O'Connor even attended Mr Donkersley's daughter, Millie's first birthday.
Mr Donkersley said Mr O'Connor's bravery award was "fully deserved".
"I think about it every day. To think what he did, it was dark and I don't think many other people would do that."
"I appreciate what he's done so much, and allowed for me to have a family. What he did was pretty special," he said.
Mr O'Connor said he was "pretty chuffed" to be awarded the bravery medal.
"I suppose because it's public you tend to feel a little bit embarrassed, but it's nice it's really nice, and strange."
Mr O'Connor recommended to anyone who ever got into a water rescue situation, to relax and side-stroke.
"It's the only way to survive."
Mr O'Connor and his wife Sandra had their bags packed to leave on a flight last night for Denmark to see his son Ricky, who has terminal cancer.
Ricky was given 24-hours to live in February, but Mr O'Connor said his "willingness to live" had kept him strong.