Complex sentence: The ground beneath the lake is owned by the shareholders of the corporation, including 690 lakefront property owners and another 515 families who belong to one of 20 waterfront easement associations.
Split into simpler sentences: The ground beneath the lake is, in fact, owned by the shareholders of the corporation. There are 690 lakefront property owners, and another 515 families who belong to one of 20 waterfront easement associations.