RedactedNarrative: On 08/26/2014, at approximately 2131 hrs within Glen Canyon NRA, Ranger and I were dispatched by patrol boat to Anchovy Point to respond to a vessel that grounded on a rock.  When I arrived to location of the incident, I observed a vessel at rest, on top of a submerged rock with 7 individuals on board.  I contacted the group and instructed everyone to don a life jacket.  THen, I assisted 6 individuals on to my patrol boat.  THe operator of vessel assisted by with securing two anchor lines off the point and starboard stern end of vessel to stabilize the vessel overnight.  Then OPERATOR1 and I boarded my patrol boat.
  OPERATOR1 stated that his group was traveling from Antelope Point back to their houseboat near Wahweap Marina when he hit a rock, which grounded his boat.  
  Through my investigation, I determined that the vessel grounded on a subsurface rock directly in the path of travel of the vessel.  The vessel contacted the rock with its keel, from bow to approximately three quarters of the length of the vessel.  The stern end was completely lifted out of the water when the vessel stopped.  The accident occurred outside the clearly marked navigation lane.  The hazard area was clearly marked with a United States Coast Guard approved Hazard Buoy.  The Hazard Buoy was within approximately 60ft of the accident location.  I was unable to see and assess the damage to the keel of the vessel because it was still submerged in the water.  However, due to my experience with similar boat accidents, I can assume that the collision with the rock caused significant damage to the fiberglass of the ship''s hull.  There were no signs of flooding on board the vessel.  I determined that the accident occurred due to the decreasing water level of the lake, lack of knowledge of lake hazards, and the limited visibility of the night.  No injuries were reported.