Abstract

Underwater communication has been a focal point of communication research, driven by a multitude of applications including underwater facility maintenance and marine exploration. However, current systems often require expensive specialized equipment, rendering them less accessible. In this paper, we break the norm by pioneering the use of Commercial Off-The-Shelf (COTS) smartphones for underwater optical communication, leveraging their built-in flashlight and camera. Contrary to prevalent belief that scattering has a negative impact on communication, we discover that scattering in water can provide a positive gain for camera-based optical communication. Based on this insight, we present and implement U-Flash, a novel system encompassing a Fresnel lens plugin design to enhance light directionality and a tailored encoding-decoding scheme optimized for underwater environments. Comprehensive experiments demonstrate the effectiveness of U-Flash, achieving significant improvements in communication distance, reliability, and data rate. Specifically, the achievable communication distance is improved from 2.4 m to 7.6 m during daytime in the presence of strong ambient light interference and further extended to 9.8 m in low ambient light scenarios at night.