...Bill Parkinson, a physics professor at the University of Michigan
Had copper wire sewn in a zigzag pattern into a rubber mat,mounted on an aluminum plate. Such that when a swimmer pressed the mat, the wires would touch the aluminum plate, thereby completing a circuit and triggering an electrical timepiece and placing system. Parkinson attached a second sheet of rubber over the first to ensure insulation. Parky filled the pad with non-conductive, silicone oil. The oil neutralised the water pressure, keeping it from closing the circuit, but offered no resistance to a hand touch... In full use since the 70's.