AquaHelper: Underwater SOS Transmission and Detection in Swimming Pools

Drowning incidents can occur in swimming pools even with professional lifeguards present. This is because drowning swimmers often face difficulties in calling for help due to choking, making it challenging for lifeguards to recognize them and provide a timely rescue. To address this problem, this paper presents AquaHelper, an underwater SOS system that can transmit and detect acoustic SOS signals in swimming pools. Specifically, a wearable device (e.g., a smartwatch) serves as an underwater SOS transmitter, with which a swimmer can call for help in emergency situations. Multiple underwater acoustic receivers are deployed to detect SOS signals and promptly alert lifeguards. The main challenge lies in the low transmission power of lightweight wearable devices, which poses difficulties in detecting weak SOS signals, particularly in low-SNR underwater scenarios. To achieve reliable underwater SOS detection, AquaHelper develops novel techniques (e.g., incorporating high-order harmonics, multi-scale window aggregation, and coherent combining of multiple receivers) to fully leverage the spectral, temporal, and spatial diversity of underwater acoustic signals. We also describe lessons learned and our solutions to address practical challenges involved in underwater SOS transmission and detection. Our experiments demonstrate the effectiveness of AquaHelper in detecting SOS signals in typical swimming pool environments.