I was going nuts.
My floating fly line was not. I cleaned it with the Glide line cleaner. I cleaned it with the Orvis Zip Line stuff. No joy. The last 5 feet or so would still sink and hover about a foot below the surface. I was concerned that the line was defective and spoke to the guys at Bass Pro about it. I remembered from when I was a kid and did my first, very brief foray into fly fishing that there was some kind of a paste you had to put on the line to make it float. The Bass Pro guy did not know what I was talking about and just recommended I clean the line.
Later, I was browsing in a different Bass Pro shop and ran across a paste floatant from Loon that advertised that it was also for lines. Of course, I realized that any floatant would probably do the same and looked at the packaging for some of the other stuff. Sure enough. You can use most of this on both your dry fly and the line. Hoping ahat this was the solution, I picked up a small container of it. I got the paste stuff because it just feels more aggressive to slap a good smooth coat of it onto the tip of the line. I would be concerned that the liquid stuff would just wash off after a few casts.
It works like a charm! The end of my line floats just fine now. This is more important when the water is running fast - the current tends to pull it down. Since I enjoy nymphing, I did not appreciate what this did to warn the fish or destroy my drift!
So - new guys - if your line sinks, just get this stuff.
Here's a generic link to the kind I got - Loon Payette