Due to the tragic events of September 11, 2001,  access to the cavern near Hoover Dam has been suspended indefinitely for security reasons.

The Hoover Dam cavern is located on the Nevada side of Black Canyon (its approximate location is indicated by a red arrow in the reference photo below.)  The entrance to the cavern is approximately 60'-70' beneath the surface.  A cable connected to a large steel plate (on the bottom) and an air filled  55 gallon plastic barrel (beneath the surface) provides a vertical line in front of the cavern entrance.  There may be a horizontal line extending into the cavern (approximately 40'.)  This line is occasionally pulled loose or may be missing altogether.  When all the way into the cavern, one can look back  and see the entrance (provided there is available daylight.)  Access to this site is via boat only.

Boats usually anchor near the rock slide area to the left of the cave entrance.  This is a steep slope that eventually drops off into very deep water so avoid leaving boats unattended. 

The floor of the cavern is a steep gravel slope that also drops off into very deep water.  Because of the depth near the cavern entrance and the overhead environment, this dive should be attempted by experienced divers only.