Praise and confidence are key words. Nothing succeeds like success. Your local Golden Retriever club should be able to advise you on this. Unfortunately, not all Goldens are Retrievers. The dog may simply lose interest in retrieving, or develop the bad habits of grabbing, biting or refusing to let go of an object.
M ake the introduction to water as pleasant and as enjoyable as possible.
A warm day and a clean pond or a quiet stream with a firm bottom no deeper than the puppy's elbows is perfect. Throw a few short retrieves on shore, and then toss the bumper just far enough into the water that the puppy has to get his feet wet. A t this point, toss the bumper out a few inches beyond his reach, so that he has to give that last push to reach it, and actually finds himself floating. Give him lots of praise. If your best efforts don't succeed in getting the puppy motivated enough to swim by himself, carry him out into water deep enough for him to have to swim.