following these events, the shogunate imposed a system of maritime restrictions (海禁, "kaikin"), which forbade contacts with foreigners outside of designated channels and areas, banned christianity, and prohibited the construction of ocean-going ships on pain of death. the size of ships was restricted by law, and design specifications limiting seaworthiness (such as the provision for a gaping hole in the aft of the hull) were implemented. sailors who happened to be stranded in foreign countries were prohibited from returning to japan on pain of death.