For port and airport construction works, site work control and quality control are generally conducted through direct measurement or direct visual observation by divers, and visualization using optical underwater TV cameras or ultrasonic instrumentation technology. For improvement of efficiency and accuracy of these works, development of visualization technology applicable in turbid water is required. The visualization technology in turbid water is also an issue to be solved for remote control of underwater construction machines from ships. Underwater TV cameras are generally used as a means to visualize images of underwater objects. However, in areas such as bays, river mouths, and port and harbor construction sites, the range of visibility is extremely short due to high turbidity and low transparency, and these underwater cameras can see only over a short distance. With these requirements, we began developing an apparatus for imaging underwater objects using ultrasonic wave which can propagate even in turbid water. The main result by the water tank experiment is as follows.
　1.The position of the lamp was able to be displayed by using the prototype.
　2.The outline of the object was not able to be displayed by the prototype.
　3.The following is necessary for reducing the change of the reproduction image.
　The amplitude of the ultrasonic wave pulse should be kept constant.
　It is necessary to use the amplifier with a wide dynamic range.
　4.The method of obtaining the vertical direction resolution uses the pulse, and when the object is scattered, is effective.