That is a beautiful body of water Jadog, I would put a subtle berm around the topside of the beaches to divert water from running straight down across it and eroding the sand quite as fast and find something to build a berm of some sorts to hold as much sand as you can at the toe of the beach under water, I do believe tho, under best case scenario, it will be somewhat of an ongoing chore to keep it looking beautiful, such as adding sand periodically. but that's not the end of the world, or too much of a problem, I think you will get tons of enjoyment out of it over the years. Good Luck!
