Top seeds Evandro Goncalves Oliveira Junior and Bruno Oscar Schmidt of Brazil cruised into the first knockout round with two victories at the International Volleyball Federation Beach Volleyball World Tour event in Portugal.
The Brazilian pair won both of their matches in straight sets to progress from Pool A.
Oliveira and Schmidt defeated Portugal's Roberto Reis and Fabricio Silva 21-10, 21-15 before they overcame Adrian Heidrich and Mirco Gerson of Switzerland 21-17, 21-13.
Theodore Brunner and William Reid Priddy of the United States topped Pool D as they beat compatriots Jacob Gibb and Taylor Crabb 21-17, 21-17 and Russian youngsters Maxim Sivolap and Artem Yarzutkin 19-21, 21-14, 15-6.
Legendary Spaniards Pablo Herrera and Adrian Gavira produced a superb display to defy the seeding in Pool F.
Herrera and Gavira, seeded 11th, battled to a 21-19, 25-23 victory over Qatar's Cherif Younousse and Ahmed Tijan in their opener and despatched Australia's Cole Durant and Damien Schumann 21-9, 21-14.
There was a surprise in the women's tournament as second seeds Barbora Hermannová and Markéta Slukova crashed out at the second-round stage.
The American pair of Kelley Larsen and Emily Stockman beat the Czech duo 17-21, 21-16, 15-10.
Agatha Bednarczuk and Eduarda Santos Lisboa won an all-Brazilian affair as they ousted Barbara Seixas De Freitas and Fernanda Alves 21-12, 21-13.
The tournament continues tomorrow.