Ok, I've had Brittanys for over 25 years now so I might be able to offer a suggestion or two.

Many people think that because 'a gundog is a gundog' that things such as swimming, retrieving, etc come naturally & therefore there's no work needed from the owner.
With some dogs that's true. You do get those that love to swim & retrieve from a very early age, but you also get those that lack a bit in desire &/or confidence.
That's not a problem, as his trainer it's your job to instill that confidence.
Britts aren't the most natural of retrievers. Yeah they'll do it, some do it very well, but they certainly aint Labradors.

There's no point trying to get a dog to retrieve if he's worried about keeping his head above water. So confidence with swimming is a first priority.
Now we've all seen & heard of the guy that throws his dog in to teach him to swim.
Nothing could be worse for a dog.
Can you imagine the sheer terror the poor, young bloke must go through as his trusted & loved owner heaves him into the unknown?

If you want to build a dog's confidence swimming then be prepared to get in there with him.
Nothing will give him more confidence then his master being there with him, to protect him as he starts out. If it's too strong for you to swim in then it's too strong for a starter dog to learn in.

So, get in there & have fun with your fella. Help him enjoy the new experience & show him there's nothing at all to fear. Give him time to learn & with you beside him he'll gain confidence & grow to love water work.
Then he'll take to retrieving with relish & eventually make a fine duck dog.

Bill Allen
Melbourne Australia.