RedactedNarrative: Operators of both boats are related and were operating on Castle Rock Lake in the area approximately 1/2 mile west of the intersection of Co Hwy Z and Co Hwy F in Adams County.  The operator of boat B was following the operator of boat A when the operator of boat A slowed the machine due to significant wave action.  The operator of boat B was traveling at approximately 3/4 throttle and was unable to slow, stop or turn the machine before striking the right rear corner of boat A.  The operators and passengers of both boats were ejected into the water.