RedactedNarrative: V1 and V2 were both traveling North bound on the Colorado River near Davis Camp North Beach, Mohave County, Arizona near the Arizona shoreline.  V2 slowed down for an unrelated vessel leaving the shoreline.  V1 was following V2 too closely and was unable to turn to avoid colliding with V2.  The operator of V2 was transported to Western Arizona Regional Medical Center and then transferred to UMC in Las Vegas.  He was released the next day.