The others have stated the case for using a collar better than I can. However, the thing that bothers me a little is your statement above about using it in "too rough water". In my mind, if the water is so rough that you would have to force a properly trained dog to go in, or continue, then you should have second thoughts about sending your dog in to start with. Our dogs aren't invincible. If it's that rough, retrieve the duck with your boat.