LONDON — Breeja Larson pretended the 12,000 fans in the Aquatics Centre and the millions watching on television hadn’t witnessed her mistake. After jumping in the water prematurely, the former Centennial High student and current Texas A&M swimmer smiled nervously, thinking maybe she was DQ’d. She then gave a thumbs up before climbing back onto the block.

Larson had hoped to live her dream Monday night in the 100 breaststroke. Instead, she had every swimmer’s worst nightmare.

“I took my mark,” Larson said. “I always like to get my mark ready. The beep went, and I think it’s just a swimmer’s reaction to just dive in and go. I kind of noticed out of the corner of my eye that nobody else went so I kind of came up. I’m glad I didn’t keep swimming. My heart sank at first, thinking: Did I get DQ’d? So I came up and didn’t say anything. I just kind of pretended it didn’t happen. Nobody saw that, right?”

An official’s mistake made Larson jump, as he sounded the buzzer before ordering the swimmers to take their mark, so she was allowed to continue. But she admittedly was discombobulated, and she finished only sixth.

“I think the jumping in early kind of messed with me a little bit mentally,” said Larson, who attended high school in Boise but moved to Arizona to train for swimming and graduated from school there. “…I feel like I would have swam better if that didn’t happen. I think I got really anxious and went out too fast and used too much energy in the first half.

“But I’ve still got a lot of time to swim (in her career). That was a great experience. You have to make some mistakes before you get them all right. It’s kind of a bummer that it happened here at this time, but it’s not the end. I’ll keep going.”

Larson, a soon-to-be junior at A&M, hadn’t even expected to be here. She has been swimming competitively only three years, taking up the sport as a senior in high school.

But, at the U.S. Olympic Trials last month, she upset Rebecca Soni, the best breaststroker in the world, and world-record-holder Jessica Hardy. Her 1-minute, 5.92-second time from the trials would have been good for the bronze at the Olympics, but Larson swam only 1:06.96 on Monday.

Lithuanian Ruta Meilutyte, who is only 15, won in 1:05.47, with Soni second (1:05.55) and Japan’s Satomi Suzuki third (1:06.46).

Soni said she is unsure if Larson’s premature dive affected her race, but she has no doubt Larson was out of sorts after the miscue.

“I kind of was like telling her in my head, ‘Don’t go!’ ” Soni said. “I wish she hadn’t jumped in. I think it deterred her from her race.”

Live and learn, Larson said.

“It’s just kind of like you appreciate the good things when bad things happen," Larson said. “You don’t appreciate your toes until you stub one. I think the next time I race this, it’ll give me the confidence saying, ‘You know you made this mistake at the Olympics. If you can get over that, you can get over anything.’ I’ve just had so many of those where something happens, and you just have to move on, and then it gets better from there.”