Russians Denis Shekunov and Dmitrii Veretiuk had mixed fortunes as the main draw matches of the International Volleyball Federation Under-21 Beach Volleyball World Championships began in Udon Thani, Thailand.
The reigning under-19 world champions came through three qualifying rounds yesterday to earn their spot in the pool stages but came unstuck against Brazilian pair Renato Andrew Lima de Carvalho and Rafael Andrew Lima de Carvalho, who won 21-15, 21-16.
The Brazilians followed up with their second win of the day, a 21-15, 21-12 victory against Norway's Karl Jørgen Mosvold and Åsmund Lyngve Vingen Sunde.
Shekunov and Veretiuk did post their first win in Pool B thanks to a 21-14, 21-14 win against Martin Iglesias and Vicente Orlando Dorguett Torrealba from Chile.
Timothy Brewster and Adam Wienckowski from the United States enjoyed a double victory on their way to the top of Pool F.
They cruised to a 21-10, 21-13 win against Moussa Idrissa and Boureima Moubarak of Niger before dispatching Japanese pair Rikuto Goto and Ryuichi Adachi 21-18, 21-9.
Thai pair Yodsaphat Pakham and Chanthira Khanok brought cheers and celebration from a packed-out Thung Si Mueang centre court as the duo dominated in a straight sets win against Algeria's Melissa Soualmi and Salima Bechar.
The 21-5, 21-9 victory puts the eighth seeds top of the women's Pool H alongside Cao Shuting and Dong Jie of China, who recorded a 21-16, 21-19 triumph against Chinese Taipei's Kung Shih-Wen and Yeh Hsuan-Tsen.
Thailand's top seeds Pawarun Chanthawichai and Saranya Laesood dropped their opening match in Pool A as they fell to a surprise 21-18, 21-15 defeat against Germany's Hannah Ziemer and Hanna-Marie Schieder.
United States pair Isabelle Bauman and Teagna Defalco enjoyed a straight sets 21-12, 21-17 victory against Yingpeng Wang and Hong Xie of China.
They are joined at the top of Pool D by Argentina's Brenda Churin and Victoria Galdon, who recorded a 21-17, 21-13 win over Australian duo Rebecca Ingram and Alisha Stevens.
Russians Anastasiia Frolova and Aleksandra Ganenko could not follow up their qualifying victory as the main draw got underway.
They succumbed to a 34-32, 25-27, 15-12 defeat against Brazil's Victoria Lopes Pereira Tosta and Vitoria De Souza Rodrigues in a marathon contest.
Youth Olympic Games gold medallists and reigning under-19 world champions Mariia Bocharova and Maria Voronina of Russia started their campaign with a 21-12, 21-16 win against Canadians Iris Fletcher and Abbey Thorup in Pool C.