This report describes the result of preliminary experiment for the development of ultrasonic prospecting and inspection technics for offshore underwater constructions, and also outline of design of these experimental facilities. These facilities began to be built from 1979, and the experiment were carried out in this year.
　They are made up of a water tank and a pressure tank. Typical characteristics of these facilities are:
　water tank
　diameter　5m
　height　10.5m
　shape　cylinder-type
　pressure tank
　diameter　4m
　maximum pressure　10kgf/cm2
　Some preliminary experiments were carried out in order to get some data for planning of model expeeriments in these facilities. This report is written for the purpose of keeping design data of these facilities and reference data of technical developement.