Allison Schmitt anchored the Americans to Olympic gold in the 4x200 meter freestyle relay on Wednesday.
Schmitt charged down Australia's Alicia Coutts to take gold for the United States in 7 minutes, 43.92 seconds, an Olympic record.
"I knew it was going to be close," Schmitt said.
"I was just trying to swim my own race and save legs on that first 50m, just like I did last night and bring it home strong for the US."
Coutts, meanwhile, focused on the positives.
"I got a phone call at quarter past twelve today telling me I was in the relay. I was a bit nervous coming in. Hopefully I made the girls proud with what I did."
The Australians, who won the 4x100m relay on Saturday, clocked 7:44.41, while France, the early leader, hung on for bronze in 7:47.49.
