After becoming shogun, he strived to ensure maritime safety by creating a position called 'Kujirabune Sayamawashi Goyo' to use kujirabune (traditional Japanese ship used for whaling) when a river flooded, to save victims and retrieve cargoes and rubbishes flushed into the gulf of Edo.
将軍就任後、河川氾濫による被災者の救出や、江戸湾へ流出した河川荷役、塵芥の回収に、鯨舟（古式捕鯨の和船）を使い、「鯨舟鞘廻御用」という役職を設けて海上保安に務めた。