Abstract: The disclosure pertains to a device for detecting sudden or slow immersion of a body into a swimming pool. More specifically, the invention pertains to a device to detect the accidental immersion of children into swimming pools. In a first embodiment, a first chamber is submerged in the water, and communicates with the water through tubes, so that disturbances in the water not caused by the immersion of a body are damped. A second chamber is in communication with the first chamber and has a sensor disposed inside it. The immersion of a body in the water causes a variation in the air mass contained in the chambers, which is sensed by the sensor which then sounds an alarm.