A standard viewing device used on a submarine is a periscope.
A periscope.
Ballast tank
scope
Submarines don't have windows, at least not any that are used for viewing outside of the hull while submerged. They are used in some submarines as bridge viewing windows, but they're subjected to ambient sea pressure when the boat submerges, not direct sea pressure like the hull is.
ASDIC
Sonar is used to detect other vessels or ships/submarines through a tube-like device> Andrea
That would be scope.
That would be scope.
That would be scope.
Zoetrope
This sounds like it's probably the sonar system of a submarine.
well i can tell you what it is but im not quit sure what you mean by an example.... it is a optical instrument for viewing objects that are above the level of direct sight; mostly used in submarines