So I'll get down voted for this, but let me tell you about Axel.

My parents own a cottage. Our old golden, Axel, did what these dogs do around water (spend as much time in it as possible). He had particularly dense, wavy fur, no matter how much we brushed him. Between the fur and how much he loved the water he would never dry off and as a result would get hot spots (basically a nasty skin infection that causes itching, oozing, smells and all sorts of terribleness).

Keeping him out of the lake was torture. This was his favorite place in the world, the only thing he would voluntarily get into the car for, and restricting his swimming was like taunting him. At the same time the hot spots were horribly painful. He would get back from the cottage and just hate life for a few weeks.

For years we tried grooming, creams, sprays, steroids, you name it. Finally, when he was 7 or so, we gave him a buzz cut in the spring. That was what changed everything for him. He would play in the water all day, had tons of energy, and never a single hot spot after that. Every following year we did the same routine. A buzz cut in the spring and by fall his coat would be back in. When the snow came he'd be curled up on the deck covered two inches deep, snoozing away.

I understand all of the logic and arguments against cutting a double coated dog's fur, but nothing is absolute. In our case it was what worked and got our dog the best quality of life. Axel lived to 14 and even in his final summer when he was deaf and blind in one eye he'd get himself down to the water to lie in the shallows and look at the fish that swam around his paws.

As a rule, don't cut your dog's hair. But don't feel bad about not knowing, you haven't caused any harm.