RedactedNarrative: V1 AND V2 WERE TRAVELLING UP THE ARIZONA SIDE OF THE RIVER.  V2 SWERVED TO AVOID ANOTHER VESSEL TRAVELLING NORTH AND SLOWED DOWN.  V1 WAS APPROX. 10-20'' BEHIND V2 AND WAS NOT ABLE TO STOP BEFORE STRIKING V2.  BOTH PARTIES WERE UNINJURED.