Surf waves, trapped in a U-shaped trough hung on the sea side of the concrete pier, can feed water through a pipe to the south side of the pool, flushing it. If the trough bottom is open, except for narrow edges, the surf will rise and fall inside. If a non-floating dense Fiberglas board lays on the bottom edges, water will be trapped in the trough when the surf recedes. The trapped water flows through a pipe inserted in a hole bored through the dirt or concrete on the south end and dangled down to and under the south-side sand. Several connections feed water through pipes pointing north under the surface.
A quicker and simpler flushing solution is to use an electronic motor-driven water pump to feed a trickle of sea water to the rocks during the day before the animals' night roosting. A float moving up and down in the surf can operate a pump. A cable anchored to a railroad car axle with wheels can hold the pump. The float moving up in the surf pulls the pump. An electric clock triggers a bypass valve to control the flush time.
Meanwhile, the sea lions and birds draw the tourists.
Max Treece, engineering physicist