Ed McKeever stormed to gold for Britain in the 200m kayak sprint at Eton Dorney.
The 28-year-old canoeist from Bradford-on-Avon, Wiltshire, led from the start as he powered over the line ahead of Spaniard Saul Craviotto Rivero and Canadian Mark de Jonge.
He punched the air as he crossed the line, splashing water at the side of his boat after winning gold. There was a slight headwind on the lake which meant his winning time of 36.246 seconds was slower than both the times he recorded in Friday's heats and semi-final.
McKeever said he woke up at 5am "like a kid at Christmas wanting to open my presents".
"I am going to get that present in a minute," he told the BBC before his medal ceremony.
McKeever said the race was "really painful" and a headwind made it feel "that bit longer".
"I was really just focused on the first two or three strokes and I wanted to nail those and get out cleanly," he said.
Asked how he was feeling as he crossed the line, McKeever said: "Just relief. It sounds strange. Not elation, more relief and so happy I could do it in front of the home crowd - it's brilliant."
Asked how he felt about being dubbed the "Usain Bolt of the water", McKeever added: "Luckily I have the gold medal to go with it now. I am more willing of that tagline.
"I am just so pleased that I could do well. I was really buzzing, in the zone and wanting to do well. I haven't made any long term plans yet. It could still go either way. I could have a career ahead of me but I am just waiting to see how I feel after this."