"I enjoyed it," he said. "I enjoyed seeing Celine fight it off as well as she could and recover very well after she capsized."
"I came here to support Celine. I was curious about how she's been enjoying herself generally over the games and to see if she's learnt a lot."
HRH Crown Prince Frederik watched the races from a VIP spectator boat, unbeknown to Carlsen, who is 4th overall on 53 points going into the final day of sailing.
"I didn't even know he was out there watching me," said Carlsen.
"I didn't expect him to come all the way down here, so it was a nice surprise".
"He's just really nice and so down to earth, just like any other random guy. When I finished he said to me, 'Well done on your race, it's a shame you capsized!'"
The Crown Prince looked excited as he got out on the water at the National Sailing Centre at East Coast Park.
A member of the IOC since 2009, he competed in sailing at the Sydney 2009 World Masters Games and was tching to get out and compete.
"It's the first time [for the games] obviously," he said. "But the Games are very good. If I could get out there right now and have a sail I would."
To follow racing sign up to the race Twitter feed, access photos and results on the Sailing competition at the Youth Olympic Games website visit: www.sailing.org/yog