How should I get my long-haired Chesapeake Bay retriever groomed?

I have a 4 year old Long haired Chessie and his coat is getting a little ridiculous. Other than around his ears and tail (which normally I take care of) , his coat is getting a little uncontrollable. I was just wondering if there is anything that I can do to shorten his hair even by just a little bit, just so that it isn't so mangy looking. Now I have done my research and I know that all out shaving him is not good, but is it alright to just shave a little bit off. Also how often is it ok to bathe him. I also know that it can be detrimental to his health if he is bathed frequently, and that swimming is the best option for a bath. And while he does swim at least once a week, the only real lake that we have access too definitely leaves him smelling like stale water. Any bit of advice would be greatly appreciated, and I thank y'all for your time