Stupidly obvious question, but do you clean your fly lines with any regularity?
After years of not giving a :holy:; when fly lines broke the $50 barrier, I figured it was worth my while to start taking care of them. Now I clean them after EVERY use, the way the manufacturer recommends which is with plain soap & water. After cleaning, I dress them LIGHTLY with the
manufacturer's recommended dressing. Except under extremely dirty water conditions, my lines give me excellent performance. The whole process takes me about 7 minutes to do.
There are plenty of cleaning products out there if you want something more exotic than plain soap & water. Lost of folks swear by
Zip Cast or other goops but I like to use what the line manufacturer recommends. Zip Cast is a cleaner & conditioner that takes only a minute to use although it is probably best done at the end of the day.
If you do clean your lines regularly and this still happens, you might want to consider looking into the
Rio Wonder Cloth. They are small, cloth-like pads that are MILDLY abrasive and come in a pack of 5. They are similar in texture to the Sci-Angler's cleaning pads minus the sponge part. The theory with the abrasive pads is that a light abrasive rub restores the finish on the line and allows the manufacturer's impregnated line treatments to come out of the plastic.
With the Wonder Cloth, if your line gets dirty midday; you can take one of the cloths out of your vest pocket, wet it in the crick and pull your line though it a few times to clean it. I just bought some myself and haven't tried them yet but others who have, swear by them for cleaning lines and all sorts of other stuff like cork grips.
BTW - they AND the Sci-Angler's cleaning pads are considered fine to use on Rio & Sci-Angler's line BY THE MANUFACTURER'S. I can't speak to any other brand lines because that's all I use.
If you're still not happy after all of that, buy a Sharkskin. They supposedly float extremely high...
...almost as high as their price!
Good luck!