(owners of beach front property sued local government and state claiming that beach restoration projects involving placement of sand along beaches seaward from mean high-water line (which was the boundary between state's submerged land and owner's properties) were unconstitutional takings of their private property, but FL Supreme Court held that no taking occurred; U.S. Supreme Court affirmed - change in mean high-water line resulted from sudden avulsion rather than gradual accretion, thus newly exposed land remained property of state since boundary remained fixed).