In a fascinating debut for the first mixed-gender swimming event in Olympic history, Great Britain took the gold medal in world record time thanks in large part to an X-factor breaststroke leg from Adam Peaty.
Peaty swam his leg in 56.78 as Team GB lowered the world record to 3:37.58.
China followed 1.28 seconds later for the silver as Australia took bronze.
Watch all the action from the Tokyo Games Live on NBC
The United States, the strategic outliers of the race, finished fifth in 3:40.58. The U.S. was the only team to tab a woman, Lydia Jacoby, for the breaststroke leg and man, Caeleb Dressel, for the anchor freestyle leg.
During her swim, Jacoby's goggles became dislodged off her eyes, though it did not slow her down significantly as she completed her leg just .14 slower than her gold medal-winning 100m breaststroke final time.