What are the duties of the first mate and the second mate on board? What function?

The first mate's simple understanding is that when the captain can't command, the first mate can take over the command of the captain, but the first mate can't, so the second mate will be on it. Of course, this kind of situation will hardly happen in reality. Even if the ship sinks, even the first mate has no chance to be promoted to captain. Therefore, the first mate, the second mate and the third mate all have their own specific responsibilities. Of course, when the captain doesn't show up when he is sleeping or sick, if the first mate is there, the first mate is the commander.

The second mate is second only to the captain and the first mate. Under the leadership of the captain and the first mate, perform the duty duties stipulated in navigation and berthing, and be responsible for driving the equipment. The second mate, under the leadership of the captain and the first mate, shall perform the duty of navigation and berthing and be responsible for driving the equipment. Route planning and implementation and chart correction are usually completed by the second mate. On some foreign ships, the second mate is the ship security officer entrusted by the captain, who is responsible for managing the medical equipment on board and acting as the doctor on board.