This work concerns the evaluation of the imaging performance of a range-gated underwater system in natural waters. We give a brief introduction to the imaging system including the fiber delay modifications that have been made in order to shorten the close-range imaging limit. We also describe the participation in a data collection effort made in the NATO SET072/RTG40 to acquire imagery from several range-gated underwater systems in various water conditions. Imaging performance of the range-gated system is compared with that of a conventional video camera with lamp illumination, as well as with the system operated in a non-gated mode. It is seen that the two non-gated approaches give similar results, while the gated mode enables an increase in performance. The modulation transfer function, MTF, is selected as a suitable performance measure. The imaging limits are investigated and compared in turbid and clear waters. We find that the identification range, is increased by 50 % compared to conventional imaging. The detection range is shown to increase by a factor of two. The results show that the imaging of a given area by a mine-detecting ROV can be made two and a half times as fast, and with less risk of disturbing bottom sediments in the process.