While there may well be a little sodium in the boat's water, in general it shouldn't be enough to cause a problem until the filters are in need of replacement. On the other hand, a lot of LR regulars need to consider their age (and circumference) being a factor, especially since so much time is spent standing/sitting on a LR trip. For AARP types, and I'm in that category, that will often lead to moderate swelling of the ankles after a couple/few days regardless of salt intake. And while I'm at it, I'm constantly amazed by some of the guys I see in the galley dumping large amounts of salt on their meals before (yes, before) even tasting it. A shake or two of salt far exceeds any small amount of residual in the water---just sayin'.