How much fresh water (in gallons) do you need on a daily basis? Is this water for general utility use and/or for drinking? Is the primary source ocean water or some other brackish source?
If the quantity is fairly low, (under 5 gallons per day) and you have good sun exposure, space availible, a clean source of water, a solar still may work. (distillation) They are a lot of work/maintenance and temperamental.
Yes, there is quite a lot of waste with RO systems. They are incredible when it comes to their purification capabilities, no denying it, but the water waste just doesn't make it a worthwhile solution, not in my opinion at least.
Why not try a filter pitcher? I don't know any specifically for salt water, but there should be some that can handle it too, I guess. You could even install a small countertop water filter, should work just as well. With classic-style cartridges, no RO membrane involved.