After nearly two hours of racing around The Serpentine lake, it came down to a furious sprint to the finish. Eva Risztov got there first, by a hand.
The Hungarian led most of the way in the grueling Olympic open water marathon at Hyde Park on Thursday, holding off a desperate bid to chase her down by American Haley Anderson.
Risztov reached up with her right hand to touch the timing pad in 1 hour, 57 minutes, 38.2 seconds. She climbed out of the water, smiling and looking fresh as can be, even flexing her muscle for the big crowd.
Anderson was right on Risztov's left shoulder coming to the line but couldn't overtake her. The American stuck up her left hand to nick the pad four-tenths of a second behind the winner, also slapping the pad with her right hand just to make sure she locked up the silver.
Martina Grimaldi of Italy disappointed the huge crowd that lined the lake in one of London's most iconic royal parks, claiming bronze in the 10-kilometer race ahead of British world champion Keri-anne Payne.
Grimaldi finished in 1:57:41.8, while Payne's lunge for the pad was only good enough for fourth. She missed the podium by four-tenths of a second, having not only failed to give Britain its first swimming gold of the London Games but any medal at all.
The home country has just one chance left, the men's open water marathon on Friday.
Risztov was out front after the first of six laps around the narrow, 28-acre (11-hectare) lake that curls through Hyde Park, dropped back to third on the second lap, then took the lead for good on the third. She and four other swimmers eventually broke away from the pack, setting a pace that forced rescuers to pull South Africa's Jessica Roux onto a boat on the fourth lap when it became apparent she couldn't go on.
Roux was covered in a blanket and taken away in a wheelchair when she got to the shore. Brazil's Poliana Okimoto also dropped out, leaving 22 swimmers to complete the race.
There were extensive safety measures in place, with several boats tagging along beside the swimmers and plenty of lifeguards working the lake in kayaks. It was a reminder of the safety improvements implemented after tragedy struck the neophyte Olympic sport less than two years ago.
American Fran Crippen suffered a seizure and drowned during a race held on a sweltering day in the United Arab Emirates. Even more shocking: Officials didn't even know he was missing until a teammate, Alex Meyer, noticed he never got to shore. Crippen's body was found about two hours later, and Meyer hopes to carry on his legacy in the men's Olympic race.
This was the second Olympics for open water, which made its debut at the 2008 Beijing Games. While the sport is often contested in rough seas, London organizers chose a picture-perfect setting right in the middle of the bustling city.
The conditions couldn't have been better -- a sunny day with temperatures in the low 20s Celsius (70s Fahrenheit) and no waves to contend with on the tranquil lake. Thousands turned out to watch on what became a party in the park, accompanied by thumping music and increasingly desperate chants of "Go Keri-Anne!"
The crowd drifted away quietly when it was over, disappointed that Payne failed to win a medal.