A computerized high resolution ultrasound underwater triangulation mapping system has been developed for the Institute of Nautical Archaeology. This system determines the position of a mobile ultrasound transmitter using a stationary calibration ultrasound transmitter and three ultrasound receivers. All three receivers and both transmitters are hardlinked to the surface via data lines connected to an IBM PC portable computer. The receivers provide sixteen bits of resolution (1/2 millimeter) to the computer for calibration/triangulation purposes. The computer determines the location of the mobile transmitter at a frequency of ten hertz, time stamps the observations, graphically displays them in real time for shipboard/diver interactive communications, and optionally archives them for future post-processing and analysis.