Reigning Olympic champions Ruggero Tita and Caterina Banti of Italy won gold in the mixed multihull on Thursday, sailing a composed final medal race to secure another Italian victory.
Argentina's Mateo Majdalani and Eugenia Bosco held off Micah Wilkinson and Erica Dawson of New Zealand to secure silver, with the Kiwis settling for bronze in a trickylight-wind contest.
"We said to each other before we started this cycle that winning a second one was going to be much harder," Tita said, adding: "We didn't win the medal today, or this week, it's the work that we put together for the whole three years".
There was heartbreak for British medal hopefuls John Gimson and Anna Burnet, who were disqualified for being over at the start. They appeared not to realise and did not go back to re-cross the line, with officials breaking the news mid-race.
The British pair, who are due to get married next month, had been well placed for silver or bronze going into the last race and were clearly distraught to hear their dream was over.
Gimson and Burnet welcomed their Italian training partners ashore, hugging them as the celebrations began on the beach for Italy, who notched up their second sailing gold of the Games after Marta Maggetti won the women's windsurfing.
Banti and Tita said the joy at winning had been tempered by knowing their friends and rivals were out of the race.
"Even during our race we were feeling their pain," said Tita. "We know how much time they put into it and the time away from family and it's very hard," he added.
DINGHY DELIGHT
Earlier, Austria's Lara Vadlau and Lukas Maehr did enough in their medal race to clinch gold in the mixed dinghy after fighting their way up from the back of the fleet.
After a brief pause while they waited for confirmation of the points tally, the Austrians celebrated by capsizing their 470 dinghy and standing on its upturned hull, waving their flag.
Japan's Keiju Okada and Miho Yoshioka stayed near the front throughout the double-points finale to secure silver, while Anton Dahlberg and Lovisa Karlsson of Sweden picked up bronze.
Wind shifts tested the crews as they had to pick a favoured side of the course and there was joy for the Japanese and Swedish crews as they savoured their results.
Although France's Camille Lecointre and Jeremie Mion won the medal race, theyended in sixth place overall on points.