A project from Heriot-Watt University and the University of Edinburgh has now developed what it says is the first fully submerged lidar underwater transceiver system based on single-photon detection, and published the results in Optics Express. Heriot-Watt employed a CMOS-fabricated silicon single-photon avalanche diode (SPAD) detector to measure photon time-of-flight using picosecond resolution time-correlated single-photon counting, according to the project. The high sensitivity of this architecture allows it to capture detailed information even in extremely low-light conditions found underwater. “… It could be used to inspect underwater installations, such as underwater wind farm cables and the submerged structure of the turbines. Underwater lidar can also be used for monitoring or surveying submerged archaeology sites and for security and defense applications."