Other than the periscope, which was designed to be extended up above the surface of the water to see what's on top, there isn't really a way to look out of a naval submarine. There are no windows or the like.
Team Magma will not appear in the submarine but you will see them get away with it the first time. The second time you see the submarine, you have to dive to the seafloor cavern to go challenge Maxie.
A submarine.
An RC Submarine is a submarine purchased at a toy or hobby store that is run by remote control. If you want to see a sample of an RC Submarine you can find one here: http://www.amazon.com/Swimline-RC-Submarine-27-MHz/dp/B0037M4Q3A
See flying Tiger Submarine Launching Tags, anywhere from $28 to $400
See website: Submarine
See Sources and related links.
They use a periscope. See the related link for more information.
The captain of the submarine raised the periscope to see if there's danger.
Go to the submarine and press B. You'll notice you can get up there. If you are above, you'll need to explore a cave with team aqua in it.
Prior to radar, you couldn't hit what you couldn't see.
Go on the submarine. You have a ticket. Dive to the bottom and then go left to see a Nessie face in the darkness. Take a photo and go back to the pub with it.
The high profile sandwhich constructor. See Who made the biggest submarine sanwhich ever?