Here is a very simple illustration of how water ballast works on a sailboat. Many people have a hard time picturing just how water can act as ballast when water is what the boat is floating in. On a very basic and intuitive level you can see that water ballast does work just by looking at the picture. Ive seen other drawings which include info on center of gravity and righting moment arm, etc., but sometimes keeping it simple is best. Now, is water ballast better than lead? Well, yes and no. Lead is simpler and being denser, it allows you to lower the center of gravity a little (which is good). But, if you plan to trailer, dumping 2000lbs of water ballast from a H26/260 lets you trailer a boat which might otherwise be to heavy to tow. So, dont let some old salt tell you that water ballast doesnt make sense.