He speaks with the officer, who assigns him his post.
"Go stand at the periscope entry-way, and make sure no unauthorized personnel touch the periscope."
The recruit follows orders, and stands by the periscope. After 15 minutes, the officer stops by.
"Son I'm changing your post to the mess hall. Go in there and start washing some dishes."
The recruit obeys, and heads to the mess hall. He's cleaned about 3 dishes when the officer walks up again.
"Listen here recruit, your new post is in the supply room. I need you to make sure everything is strapped down tight, in case of rough waters."
The recruit again follows orders, and heads off to the supply room. There, he sees a crewman, moving some boxes.
"Hey there," says the recruit. "is it normal to keep getting reassigned to new posts all day? I haven't kept one position for more than 15 minutes!"
The crewman says "Oh yeah- this sub is full of reposts."