Kingman Wash is located on the eastern shoreline of Boulder Basin, near the entrance to Black Canyon.  It is accessible by boat or vehicle.  Vehicle access is provided via a gravel road that links to U.S. 93 a few miles south of Hoover Dam.  I've made only two dives in this area (both from a boat,) so I cannot attest to shore diving conditions near the vehicle parking areas.  The boat dives were along the shoreline near the south side of the bay.  A steep slope with many large boulders made for an interesting dive.