Cap'n...there is no coast guard certification. Perhaps you are referring to the classroom sailing course run by the CG Auxilliary in many places. This is an excellent course and at the end of it you do get a certificate which is useful if you want to charter a boat. More important...it teaches you the rules of the road and basics of sailing and coastal navigation...but there is no "on water" component. You don't "need" any type of certificate to go sailing.
The coast guard captains course (6-pack) is more geared to those who plan to take on charter customers or drive boats professionally. It is not for beginning sailors.