A more thorough explanation:

A shipmaster is the commander or captain of a merchant vessel. They are responsible for the navigation of the ship and the safety and well-being of the crew and cargo.

For example, if a ship encounters rough weather, the shipmaster must make decisions about how to navigate the ship safely and ensure that the crew and cargo are secure. In addition, the shipmaster is responsible for ensuring that the ship complies with all relevant laws and regulations.

Under maritime law, the shipmaster has significant legal responsibilities and can be held liable for any damage or loss that occurs as a result of their actions or decisions.