Cunha qualified for the 2008 Summer Olympics in Beijing, after placing tenth at the FINA World Open Water Swimming Championships in Seville, Spain. She became the youngest-ever swimmer to participate in the inaugural women's 10 km open water marathon, against a field of twenty-four other competitors, including her teammate Poliana Okimoto, South African amputee Natalie du Toit, British duo Keri-Anne Payne and Cassandra Patten, and sixteen-year-old American Chloe Sutton. Cunha finished in a close race for fifth place, with a total time of 1:59:36.8, approximately one second ahead of Switzerland's Swann Oberson, yet nine seconds behind winner Larisa Ilchenko of Russia.