Thomas Finchum performs a dive in the preliminaries of the men’s platform at the U.S. Olympic diving trials in Indianapolis on Thursday. Associated Press Photo.

INDIANAPOLIS — Thomas Finchum had just seen three 10s flash on the scoreboard — the symbol of diving perfection.

He rinsed his hair under a water fountain, rubbed down with a towel, glanced up at the 33-foot tower and mouthed two simple words.

“Go David.”

David Boudia — his training and synchronized partner, not to mention the guy he considers “a brother” — responded to Finchum’s encouragement with four 10s of his own.

“David stepped up to the end of the tower saying, ‘Thomas just set me up.’ They do that in practice on a regular basis,” said their coach, John Wingfield. “It’s fun. It’s almost like a little one-upsmanship.”

On a night that had to make the Americans feel a lot better about their chances in Beijing, the 19-year-old Boudia and 18-year-old Finchum produced one scintillating dive after another Thursday to pull away from the field and set themselves up to claim both U.S. spots for the 10-meter platform.

The finals are Sunday, and only the winner at these Olympic trials gets an automatic berth. The second spot will be chosen at a selection camp in Tennessee next month, but it seems all but assured that whoever finishes as the runner-up will be the other choice.

Boudia and Finchum, who both grew up in the Indianapolis area, wouldn’t have it any other way.

“We really do push each other,” Finchum said. “I don’t want it to be anyone else on that team with me but David. He’s like a brother. I want to beat him, but I want to support him, too.”

Boudia has totaled 1,091.90 points through the preliminaries and semifinals, guarding the lead he had before anyone took a dive. He received 65 bonus points before the competition started as a reward for his third-place finish at the World Cup in Beijing this year.

“It’s almost like performing on stage, and I look forward to showing off Sunday,” he said.

Finchum had the highest-scoring round of his career, posting 541.30 points in the semis for a two-round total of 1,065.25.

“It’s definitely exciting to get your personal best and know you can still do better,” he said. “I’ll go out there Sunday and hopefully beat that one.”

He received at least one 10 on three of his six dives, but Boudia got the best of his buddy in the fourth round.

Going just ahead of Boudia, Finchum earned three 10s for a reverse 31⁄2 somersault tuck. Then it was Boudia’s turn, and he responded with four 10s on the very same dive, known in the manual as 307C.

“I knew David was going to hit that dive,” Finchum said. “It’s one of his best dives. Once I did my dive, well, he’s thinking in his mind, ‘I’ve got to do mine better.’

“And he did.”

On the women’s side, Christina Loukas saved her best for last in the 3-meter springboard semifinals, earning mostly 9s on her final dive to increase her commanding lead.

Loukas led by nearly 30 points after the morning preliminaries, and she was even stronger in the evening session, when the scores carried over.

She totaled 729.85 points, well ahead of second-place Nancilea Foster (681.40).

Foster was strongest on her first and last dives, earning bunches of 8.5s. She closed out with a reverse 21⁄2 somersault pike.

“Even as I hit the water, I just thought, ’That is my favorite moment of diving,”’ she said. “It’s a dive that I’ve hit before in important stress situations. Just knowing I did it right is very good.”

Ariel Rittenhouse, second after prelims, slipped to third with 650.30 after botching her second dive.

Loukas, a 22-year-old who dives out of Indiana University, earned her highest marks — a 9.5 and three 9.0s among the seven judges — on her final dive, a forward 21⁄2 somersault with a twist. She’ll take a comfortable lead into Saturday’s 12-woman final.

Only the winners of the four events being contested at the trials earn guaranteed Olympic berths. The second spots in the individual events will be announced July 7 at a selection camp in Knoxville, Tenn. Top-six finishers at the trials will be invited there.

That would appear to be a mere formality for Boudia and Finchum, whose focus will soon turn to beating the powerful Chinese in their home pool.

The Olympic hosts won six of eight events at the last Summer Games in Athens, and they’re hoping for a sweep this time around. The Americans, on the other hand, are looking to bounce back from a medal-less showing in Greece, the first time since 1912 they had failed to win a diving medal except for the boycotted Moscow Games.

Boudia and Finchum want to prevent another embarrassing shutout.

“David has been able to get in there and bug them a little bit, and Thomas is certainly capable of it,” Wingfield said. “Certainly our boys have a lot of respect for their boys. I think they are starting to get some mutual respect from the Chinese.”

After the Indiana University Natatorium has cleared out for the night, Boudia walked up to Wingfield and shyly asked what dives he’d be doing in Sunday’s final.

Both agreed.

No need to change a thing.