The duo, who had won a silver and two bronze medals in the previous three events, finished sixth in Friday’s final in Merida.
Couch and Barrow could only manage a score of 285.84 points after dropping their fourth dive.
After the contest, Couch tweeted: “In sport you have your good days and your bad days. Today wasn’t mine and @SarahBarrow’s good day, but onwards and upwards.”
It meant the city pair finished fourth overall in the six-leg series, with China, Canada and Malaysia finishing above them.
In Mexico, China’s Yajie Si and Jie Lian won with 333.72 points ahead of Canada’s Meaghan Benfeito and Roseline Filion, who scored 328.41.
Couch and Barrow will be hoping to bounce back in Sunday’s individual event.
Couch goes into the final leg, sitting top of the overall rankings, four points ahead of Filion. However, she has been handed a tough semi-final on Sunday. Both Chinese pair of Si and Qian Ren are in her heat, along with Canadian Benfeito and Australian Melissa Wu.
Barrow will be semi-final B, which has less divers in.
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