A capacitive relay takeoff swimming platform sensor system including multiple stations, timing devices and capacitive sensor devices where the presence or departure of a second swimmer on a relay takeoff swimming platform is sensed by the change in capacitance of a sensor mat and compared to the arrival of a first swimmer at a touchpad sensor. The system includes automatic recalibration of sensing, such that presence of a swimmer is sensed and then system recalibrated so as to detect departure of the swimmer. The sensor mat includes an polycarbonate perimeter.