Here at Stillwater, we have a real passion for saltwater fly fishing. Regularly, we host and help folks gear up for their upcoming saltwater trip. One of the most common questions is, "What are the best general-purpose saltwater fly lines?"
More than any other, I recommend the Scientific Angler, Amplitude Smooth Grand Slam. It loads, shoots, picks up off the water, and blasts through the wind on a level that is a step above every other fly line out there. I recommend this saltwater fly line for beginners learning to cast with these fast action, 8wt through 12wt fly rods. The Grand Slam series is bumped up 3/4 line-weight heavy, which makes a massive difference for the average trout fisherman, who is used to casting a much softer 5wt. The extra weight will help you load the rod more efficiently, which will also help you feel the rod's power throughout the cast, translating into a much more effective and accurate cast.
Saltwater is known for breaking down your fishing gear. The SA Amplitude series also has one of the best life expectancies of any of the fly lines we regularly use on the Flats. You have the option of Smooth vs. Textured. If you decide to go with the Textured, you should find that it will shoot the line further than the smooth. However, you might also find that the line seems to have a little more "memory" to it, which can be a bit of a hassle. The SA Amplitude Smooth Grand Slam is our most-sold saltwater line because it gets the job!