Jennifer Kessy tackled partner April Ross, who was already on her knees in the sand.
They'd just clinched an all-American final at the Olympic beach volleyball tournament.
Kessy and Ross upset top Brazilians Juliana and Larissa in three sets Tuesday night to set up a meeting with Misty May-Treanor and Kerri Walsh Jennings.
May-Treanor and Walsh Jennings, the two-time reigning Olympic champions, won their semifinal earlier in the day against Xue Chen and Zhang Xi of China.
Wednesday's final at Horse Guards Parade will mark the second time in the last three Olympics that American women will win two medals in beach volleyball.
Kessy and Ross, the unlikelier pair to make it, knocked off the reigning world champion Brazilians 15-21, 21-19, 15-12, finishing the upset in the rain on a Kessy spike.
Earlier, May-Treanor and Walsh Jennings survived for a 22-20, 22-20 win over the 2008 bronze medalist Chinese team in the first semifinal.
Ross won the second set with a spike and the Americans took an early lead in the third. Ross bounced back from a serve into the net to make two key plays: a drop shot that fell out of reach for the Brazilians, and a serve she let go long to make it 9-6.
Kessy spikes made it 10-7 and 11-9, and it was 13-10 after a Ross spike hit the tape at the top of the net and dropped on the other side.
Brazil couldn't return a serve, making it 14-10, but the Brazilians saved two match points before Kessy sealed the win with a spike.
Brazil will play China for the bronze medal, also on Wednesday.
"We relaxed in the middle of the second set and that was the turning point, the reason we lost," said Juliana.
May-Treanor, who turned 35 last week, and the soon-to-be 34-year-old Walsh Jennings rallied from behind early in the first set and late in the second to beat their younger opponents under cloudy skies.
They won the final three points of the match to avoid dropping a set for the second time in a week (and the second time ever at the Olympics).
"They were playing awesome but we made it happen. I'm speechless," said May- Treanor. "I think we played as a unit, so I'm very happy. I had a picture in my head at the beginning of the season of how I wanted us to play, and we're living that picture. But it's not over yet."