AUSTRALIAN breaststroke world record holder Christian Sprenger said he was "absolutely shocked" when he saw a Facebook post late on Tuesday night that said his long-time Norwegian rival and friend Alexander Dale Oen had died of a heart attack.
Norwegian Swimming officials said Dale Oen had been found collapsed in a shower after a training camp in Flagstaff, Arizona.
He had suffered a cardiac arrest and was unable to be resuscitated.
The 26-year-old won gold in the 100m breaststroke at the World Championships in Shanghai in July 2011 and was regarded as one of his country's best medal hopes in London.
The same age as Dale Oen, Sprenger said they had become friends and rivals a decade ago - before they even met.
"When we both started achieving good times as 16-year-olds, they'd get put on the net and we were always keeping a close eye on how each other was going," Sprenger said.
"We first raced each other in Europe in 2007. We'd both looked forward to meeting each other and we became good friends from then on."
Sprenger said Dale Oen was not only a champion in the pool, he was a champion out of it as well.
"The people you respect are those who are there whether you beat them, or you are struggling," Sprenger said.
"Alexander was one of those. He had all the characteristics of a champion."