On this day, Coach Daoge assigned a task to the two trainee submarines, Beibei and Ali, along with the underwater scooter Stone: first, return the sea cucumbers to the coral clusters, then find a suitable container to transport the eels delivered by airplane Susie back to the training base. The three companions initially competed to be in charge, nearly ruining everything. Later, they realized their mistake and worked together to finally complete the task. Submarines Beibei and Ali graduated on this day. At the moment of graduation, they reminisced about their experiences during submarine training: diving to 20 meters to rescue the coach, swapping jobs with Mother Oil... These experiences not only taught them the principles of handling tasks but also allowed them to gain precious friendships.