Periscope.
i think you mean the 'periscope'.
The object used to view the outside from inside the submarine is called a periscope.
An alidade is a sighting device for measuring angles, in fields such as cartography and astronomy.
Theodolite Alidade
A standard viewing device used on a submarine is a periscope.
The submarine is manned by the crew, and crew members are called submariners.
Asdic
The 'helmsman' steers a submarine.
Fulton designed a submarine called Nautilus.
Submarine mountains that were once active volcanoes are called seamounts.
The USN's submarine force in WWII was called the SILENT SERVICE.
The H. L. Hunley was the name of the Confederate submarine that was the first combat submarine to sink an enemy ship.