Salmo is exactly right. In my experience, braided-core lines are much more susceptible to waterlogging that solid core ones.
But it's worth remembering that not so long ago, nearly every fly line eventually sank unless treated liberally with mucillin before fishing and periodically during the day. Some silk line enthusiasts use double taper lines which they strip off the reel and reverse midway through the day. That way they're fishing with a fresh, dry tip the rest of the day.
Pick up a small container of mucillin at your fly shop (IMHO, the non-silicone formula is best) for a couple bucks. After sealing your (bone-dry) line tip with a very small drop of head cement, develop the habit of applying a thin coating of mucilin to the last few feet of your line with the little pad that comes in the container. Applying mucilin to a bone-dry line BEFORE fishing it is MUCH more effective than trying to do so midday to a waterlogged tip.
K