Second-seeded San Diegan John Hyden and partner Brad Keenan were eliminated in the biggest upset yesterday in the opening round of play in the AVP Crocs Slam beach volleyball tournament at Mariner's Point on Mission Bay.

Hyden, a former two-time, first-team all-American at San Diego State, and partner Keenan lost to the No. 31 team of Joaquin and Jonathan Acosta, up-and-coming cousins who starred for BYU and UCLA, respectively, 24-22, 23-21.

The tournament's other top-seeded teams advanced into today's play.

Women's No. 1 Jen Boss and April Ross quickly dispatched No. 32-seeded Leah Allinger and Barbara Carson, 21-10, 21-12, to move into today's round of 16. No. 3 seed and San Diegan Dianne DeNecochea and partner Barbra Fontana moved on, beating 30th seed Leilani Kamahoahoa and Angela McHenry, 21-18, 21-14.

Men's No. 1 Sean Scott and Nick Lucena also moved on easily, beating 32 seed Scott Hill and Everett Matthews, 21-15, 21-16. No. 3 seed Matt Olson, another San Diegan, and partner Kevin Wong won, beating 30th seed David Fischer and A.J. Mihalic, 21-12, 21-15.

Another SDSU alumnus, ninth-seeded Hans Stolfus, playing with Jason Ring, advanced after downing Evan Engle and Dane Jensen, 21-15, 21-16.

Today's play begins at 10 a.m. Play in the second round of the tournament, that has 32-team brackets for both men and women in a single-elimination format, will conclude at approximately 2 p.m., with third-round action following.

Tomorrow's semifinal play will begin at 11:30 a.m. with the men's final at 2:30 p.m. and the women's at 4 p.m.