We have three GSDs in the pool daily and yes, they do leave a little fur

We bought a dog dryer and blow them dry after each swim. This removes a lot of the loose undercoat and helps reduce those fur balls in the house, too. Additionally, in a humid climate the dogs never quite air dry and can easily develop hotspots and fungal infections.

We found that by using the dog dryer we have very little hair in the pool. I empty the skimmer basket directly after a swim and again a couple hours later, and the next morning I scoop yp what fur collected and dropped to the bottom.