What are the main jobs of seafarers? Please reply if you know, thank you.

The daily work of seafarers is divided into two parts, with the deck as the boundary. Above the deck, collectively referred to as the deck department. The crew of the deck department usually includes steering, observation radar and electronic charts, and then use internationally used signal flags and signal lights at the intersection of the two ships. There is an engine room under the deck. There are some instruments and equipment in the engine room, such as main engine, auxiliary engine, main boiler and auxiliary boiler, which provide normal power for the ship. The daily work of the crew of the engine department is to maintain, maintain and monitor these instruments to ensure their normal work. But to become an international sailor, you need to have relevant qualification certificates, just like having a driver's license at the beginning. If you don't have a certificate, you have to go to a maritime college to study and get a certificate. I wonder if the landlord knows this. I am a sailor on vacation. ...