In port areas, a wide-angle underwater imaging system has been in strong demand for wide-range inspections of undersea structures for periodic maintenance and for rapid checks in case of disasters. However, seawater in such areas is often turbid due to urban activities, which makes underwater imaging more difficult. We developed a three-dimensional imaging sonar system (hereinafter called System 08) for surveying of portside underwater constructions based on a prototype named System 07, which was for off-line viewing of 3-D images made in tank experiments. System 08 could be printed on-line 3-D acoustic image at 1/8 screen/0.125 sec. and surveyed height of a slope within ± 5 % or less in water tank measurement.