Would like to install an automatic pump to drain a small pit that my patio drains into. Pit is approximately 2'x3', 2 ft deep. I intend to use pea gravel in the pit, with a marble chip rock as the top layer and want to place the pump under the rocks, so it will not be seen and leave it there. Is there a pump available that I can leave in the rocks . Would like one with some sort of water level activation switch.