once again, elaine reclaimed the top prize, winning the gold in record time in the 100-meter race. i know all of us were nervous, and it s always best to come out on top. reporter: for tennis, novak djokovic is heading home disappointed. the top-ranked player lost to spain s pablo carreno busta in the bronze medal match. but the day was golden for u.s.a. swimming. caeleb dressel from the united states is going to win. reporter: on the men s side, caeleb dressel didn t just crush his competition in the pool. he set a world record of 49.45 in the men s 100-meter butterfly. we spoke to dressel before he left for tokyo, where he told us he s just getting started. i ve learned a lot about myself. there are still some things, i feel i got a lot of talent left to squeeze out. reporter: no other woman could keep up with katie ledecky as she closed out her games with