An example safety system for underwater diving includes a biological sensor for detecting a diver in distress, an alarm system, and a rescue deployment system. The sensor detects an anomalous condition and issues an alarm, such as, for example, a buzzer or a flashing light. In another example embodiment, upon determining the existence of a major, persistent, time-critical anomaly, or upon being instructed by the diver, the system inflates the diver's buoyancy compensation device and brings her toward the surface at a controlled rate. In another example embodiment, upon determining the existence of such an anomaly, or upon being instructed by the diver, the system releases a buoy, allowing the buoy to float to the water surface and alert others. In another example embodiment, the buoy detects its position upon reaching the surface and issues a radio signal, indicating distress and its current position.