Competing against swimmers with years of senior national team experience, the two 16-year-olds scored 80.6667 points in the final.
Alvarez and Ortellado had 79.7667 points in Thursday’s preliminaries to be one of 13 out of 27 duets to advance to the final.
China’s Wenyan Sun and Xuechen Huang won gold with 92.2000 points. Japan’s Yukiko Inui and Risako Mitsui finished second at 90.3333, and Ukraine’s Lolita Ananasova and Anna Voloshyna were third with 90.0000 points.
Karensa Tjoa (San Jose, Calif./Santa Clara Aquamaids) was the U.S. reserve.