Splash Down Waterpark  Splash Down Waterpark, a waterpark located within Ben Lomond Regional Park in Sudley, Virginia (near Manassas), is operated by the Prince William County Department of Parks and Recreation. The park was built at the location of the Ben Lomond swimming pool, opening in May 1996. Among slides and wading pools, the facility also houses a 25-meter competition pool. Splash Down Waterpark is the home of the Ben Lomond Flying Ducks Swim Team.