The purpose of underwater survey is to provide basic data for proper maintenance and reinforcement to detect waterborne defects as early as possible, to prolong the life of bridges and to ensure safety. This study suggests an underwater investigation item and method to be observed by the inspector in checking the substructure of the marine bridge. However, due to the limit that can not deal with the characteristics of the area where maritime bridges are installed in detail, it is considered desirable to use this point as a minimum safety and performance standard in underwater survey sites and management bodies.