Tidal Tank

Picture a large tank buried in the earth behind a marine bulkhead. The tidal exchange at the bulkhead is zero to ten feet (low to high tide). When the tide comes in, a inlet tube at the bottom of the bulkhead, connected to the tank allows the water to flow in. Opposite happens when tide goes out. Two options for power generation. One, a water turbine in the inlet/outlet pipe spins to create electricity. Two, an air outlet pipe at the top of the tank spins as the volume of the tank is displaced by the water flowing in and out. If the tank is, say, 10,000 gallons and the tidal exchange happens roughly 2x per day you could regulate the flow so that water is always moving through the system. Question is, how much power can be generated by that amount of water or air movement?