Abstract: A swimming pool alarm responsive to wave motion that will produce a signal when two waves exceeding a threshold level of amplitude are sensed within a preset duration of time. A transducer senses air or water pressure changes and produces electrical signals corresponding to the changes. A comparator system, connected to the transducer, receives the transducer signals and, if the signals exceed a preset threshold level, transmits a signal to the discriminator system. The discriminator times the signals received from the comparator and when two signals are received within a specified period of time, a third signal is generated. A warning device such as an alarm is connected to the discriminator and will be activated by the third signal.