>>3066362A deck cadet will take part in navigation of the ship. Tank cleaning, painting and other daily ship tasks. Re-rolling ropes, making shelves all sorts of shit. Deckies don't have too much to do on container vessels, except when it's coming into port. Then it can be tiresome, especially since these companies hire Romanians, Indians and shitty people like that, so there's a lot of miscommunication and accidents.
A deck officer once qualified does a lot of stuff, 2nd/3rd mate are responsible for navigation, C/O is in charge of cargo and stuff, Captain is in charge of the boat. However, with the sudden increase in technology, deck officers are being replaced. They already have ships outs there that are autonomous.
Engineers fix the ship. They are in charge of all the machinery, that includes anything from the main propulsion, main engines, all the way down to the shit tank and the lights. However again, on newer ships the amount of new tech is making us think of the future too.
There's a new rank out for officers, which is ETO. It's basically an Electrician that's an officer. However, it's more involved with the complicated systems that are put on board. Gone are the days where you can just change a part. Now you need to re program the motor to accept it. Think about an ETO like an auto-electrician. How do you think a BMW would without the computer controlling it?
I'm a 2nd Engineer with a C/E CoC. I make good bank, but If I could give any advice it would be look into becoming an ETO. In 10 years time they will be the most sought after Officers for a ship. Especially new builds.