I use alot of cdc ... loop wing emergers under wings and parachute posts.That said I would imagine its the floss soaking up water or to heavy a wire hook .Try putting floatant on the body ... I never use floatant it on the cdc .After a fish has slimed my fly i usually rinse it ,spit on it, rinse it again ,pinch the water out on a samadou pad and shake in desiccant to dry .