FWIW The sand beaches only need to last as long as the grandkids are willing to use them. I have a very well built sandbox in the back yard that I have been working on to get rid of. We only used it for abut 3 years. We nailed 4x4s together with those spiral landscape nails, and needed my spud bar and maul to get them apart. So IMHO there isn't a lot of good reason to go overboard on making a long-lasting beach unless you have a much larger family than I do.
Also, we just swim from the dock, and touching the bottom is avoided at all costs. Floats, rafts, diving platforms, small boats, etc. provide plenty of entertainment.
