Within the Japanese territorial waters, there is heavy traffic with many Japanese and foreign cargo vessels, tankers, fishing boats and other ships. Therefore, collisions and other maritime accidents occur from time to time, just as traffic accidents take place on land. When accidents happen, they may cause not only losses for ships and cargos, but may also lead to human deaths and marine pollution.

The Maritime Accident Inquiry Agency investigates and judges the causes of such maritime accidents from various technical angles in order to prevent the recurrence of future accidents. Depending on the results of judgment, the Agency may carry out administrative penalties, such as suspension of duty or reprimand, or provide recommendations as part of administrative guidance. The maritime accidents that are judged by the Agency cover those involving pleasure boats, such as personal water crafts and motorboats which are on the increase year by year, as well as those in rivers and lakes in Japan.