Not sure how visible it is in the water as I havnt field tested it yet, but I know while its on the spool you buy it on you can see straight through to the bottom. As for leaders, I will still use a fluro leader to absorb some of the shock associated with zero stretch lines. It know comes in 3lb which I found impossible to break. Im not sure where they get the breaking strains from on these braid/fusion lines, but they are a hell of alot tougher than mono. As I have said in previous posts, I will never go back to mono. Braid/fusion catches a hell of alot more fish, and allows us to use lures/plastics more effectivly, and this new fireline crystal can only be an added plus to our arsenal of weaponary to tackle these finned addictions of ours.