Olympic swimmer collapses after learning he’s disqualified for breaking little-known rule

In a moment that seemed to be straight out of a nightmare, a British swimmer learnt they were disqualified seconds after thinking they had won and secured their spot in the final race.

Even getting to the Olympics is an achievement in itself, but many athletes are rarely happy with this accomplishment unless they secure their place on the podium.

They have to make sure they're both mentally and physically ready for the mammoth task as one successful moment could change their lives.

British swimmer Luke Greenbank was hoping secure a spot in the semi-finals in the men's 200m backstroke earlier this week, but it seems this year it just wasn’t meant to be... despite it very almost being so.

Team GB swimmer Luke Greenbank. (Maddie Meyer/Getty Images)

Despite being a top contender for the event, and even coming first in the heat and beating out his competition by a clear margin, Greenbank was disqualified.

After thinking he'd secured his spot in the semi-final race, the Olympian soon realized what had happened when he looked up at the results board in a crushing moment.

He put his head in his hands and dropped to the floor upon realizing he'd been disqualified, with Australian swimming legend Ian Thorpe saying it was obvious just 'how devastated' the athlete was.

Speaking after the decision, Greenbank said: "I don't know what to say, absolutely gutted. It's really annoying, I feel like I'm on good form."

The Team GB swimmer was clearly devastated upon realizing he'd been disqualified. (BBC)

But what rule did Greenbank exactly break?

Footage of the race showed that after the 15-metre mark, Greenbank was still underwater.

A swimmer must break the water and have part of themselves above the surface by the time they reach 15 meters, and they have to do this for each lap they take.

For viewers there is a red marker that makes it clear which athletes have broken the rule.

After seeing himself be disqualified, an instant replay allowed Greenbank to see that he was still underwater by the marker, leaving no grounds for an appeal.

Fans praised Greenbank for his effort, despite the disqualification. (Adam Nurkiewicz/Getty Images)

The 15-meter rule is applied in backstroke, butterfly, and freestyle events but not in breaststroke.

On social media, fans couldn’t help but feel for the world class athlete and this unfortunate turn of events.

“Argh! That’s a nasty hit for us. Feel for Luke. One of the nicest people you would ever wish to meet!” one Twitter user wrote.

"Ugh, watching Luke Greenbank get disqualified in the Olympic semifinals is heart wrenching."

"Oh no, Luke Greenbank of Great Britain just swam the fastest time of the morning in the 200 back but got DQ'd.