A single LED and a single camera enable centimeter-accurate underwater ranging while conveying data

Underwater missions need links that carry data and geometry. We present a monocular underwater optical camera communication (UWOCC) system that performs simultaneous data reception and point-to-point ranging from a single LED. Distance is recovered from the LED's apparent size, so only one camera and one light source are required, enabling sparse, low-cost deployments. We validate centimeter-accurate ranging in two environments: (i) an indoor large tank, achieving few-centimeter error at 10 m; and (ii) a bright freshwater lake ($\sim$0.5 m depth), achieving few-centimeter error at 8 m. Per-frame precision is millimetric at long range when exposure is stabilized. This capability complements acoustic links with a short-range, high-rate, self-localizing layer.