RedactedNarrative: While on boat patrol on Sand Hollow Reservoir I was making an approach to the marina moving counterclockwise near the island.  As I came around a ledge I saw an aluminum boat with someone using a bucket to bail water out.  Someone started flagging me by hand.  I noticed their boat sagging at the rear and went closer.  In the span of about 30 seconds the boat had taken on significant water.  I radioed dispatch to page the county dive team and to bring bags to float a swamped boat.
  
  I told the driver to beach the boat since the swamping was uncontrollable  While he did that I rigged a rope to my stern.  The only place to beach was a sandstone rock under the water about 4 feet.  After he put it against the rock they got out of the boat and gathered some belongings that were floating away.  I had him hook the rope to the bow of his boat.  I knew if the boat didn't have resistance it would rock back off the ledge and sink completely.  I used my slightly over idle speed to pull his boat over the tipping point of the rock.  I notified dispatch that all occupants were code 4.  We gathered belongings and waited for the dive team.  Once on scene the dive team floated the boat and I towed it back.
  
  operator had no idea where the water came from.  He had been playing on the rocks with his family while the boat was tied off.  They got in to leave and the main engine was acting up so they started using the electric trolling motor.  The didn't strike anything but started taking on water. No holes were discovered when it was pulled out of the water.
  