The previous day's action had seen reigning men's champions Todd Rogers and Phil Dalhausser of the USA tumble out against Italy, and the shocks continued in the women's tournament when the Czech Republic's Marketa Slukova and Kristyna Kolocova produced the surprise of the women's draw so far as they defeated medal hopefuls Talia Rocha and Maria Antonelli of Brazil in three sets.
The fast-emerging Czech duo have begun to make their mark on the World Tour in recent months and have underlined their potential at London 2012, though few would have expected them to prevail in this last-16 encounter against the Brazilians.
Yet the Europeans looked comfortable as they eased to the first set and then went close to closing out the match up in two before the Brazilians took it to a decider.
Next up for the Czechs is a quarter-final clash with Jennifer Kessy and April Ross of the United States.
Also through from the USA are favourites Misty May-Treanor and Kerri Walsh, who returned to their best with a straight-sets win over the Netherlands.
The reigning women's two-time champions were on the end of a shock of sorts two days ago when they dropped a set for the first time in 17 Olympic Games matches before recovering to defeat Austria's Doris and Stefanie Schwaiger.
The USA pair were never in any danger of a repeat today, however, as Marleen van Iersel and Sanne Keizer were swatted aside 21-13 21-12.
Walsh in particular was a dominant force at the net as the champions effectively stifled the opposition and fired an ominous warning to their rivals that a third successive gold medal is very much in their sights.
'We executed really well, with smooth delivery. We forced them to make errors. That was our plan,' said May-Treanor.
China's Zhang Xi and Xue Chen made light work of Russia's Evgeniya Ukolova and Ekaterina Khomyakova to ease into the quarter-finals, while Italy's Marta Menegatti and Greta Cicolari further underlined their status as potential medallists with an impressive victory over Spain.
Meanwhile, in the men's competition, Brazilian duo Alison Cerutti and Emanuel Rego continued their perfect start with a straight-sets dismissal of Germany's Jonathan Erdmann and Kay Matysik.
The gold medal favourites were always in control of the last-16 tie and duly eased to a 21-16 21-14 victory to ensure they reach the quarter-finals stage without dropping a set.
Germany's Julius Brink and Jonas Reckermann made sure of their place in the last eight with a similarly routine win over Latvia, while the Netherlands' Reinder Nummerdor and Rich Schuil set up a quarter-final against Italy after a straight-sets victory over Switzerland's Patrick Heuscher and Jefferson Bellaguarda.
Jacob Gibb and Sean Rosenthal of the USA became the final team to book their place in the last eight with victory over Russia under the floodlights.
The USA duo are the leading team on Beach Volleyball's World Tour so far this season and their supremacy over Sergey Prokopyev and Konstantin Semenov was largely in evidence in their 21-14 22-20 triumph.