Hector Pardoe was forced to withdraw from the men's Olympic 10km marathon swim due to injury with just a couple of kilometres left.
Pardoe revealed after the race, which was won by dominant German Florian Wellbrock, that he had received a stray elbow to his face.
He admitted to the BBC: 'On the last lap, I took an elbow to the face, I thought I had lost the eye. My goggles completely came off.
Team GB's Hector Pardoe sports a bandage over his right eye after being struck by stray elbow
Pardoe shows off his battle wounds after he was forced to retire from the 10km marathon swim
Germany's Florian Wellbrock cruised to Olympic gold in Tokyo on Thursday
'I like to think whenever I get an injury I'd be able to finish the race but the goggles completely fell off.
'And I couldn't even get them. And I couldn't see anything. I thought my eye had fallen out into the water.
'And I was going up to the lifeguards saying "my eye, my eye - is it OK".
'And they weren't giving me a very decisive opinion. And yeah, I had to get out after that.'
Former swimmer and current commentator Andy Jameson, who won bronze in the 100m butterfly at the 1988 Seoul Games, posted a close-up image of Pardoe's battle wounds following the race.
He wrote on Twitter: 'Utterly brutal … Great Britain's @hector_pardoe had to withdraw from the men's Olympic Marathon Swim (10k Open Water) very close to the end after receiving a forearm smash to the eye socket!
'Nasty … especially considering he had swimming goggles on! Great effort up 'til then!'
The scorching Tokyo conditions also made it a brutal event for those competing, but German swimmer Wellbrock certainly didn't let that affect him.
The German powered his way to Olympic gold in a time of 1:48:33.7 - winning by over 25 seconds ahead of Hungary's Kristof Rasovksy Italy's Gregorio Paltrinieri.
The German made light of the scoring Tokyo conditions on Thursday at the Olympics