I think many within the community are over thinking how subs should be like if introduced in the game. We don’t necessarily need to code in ocean floors and ocean life in the game like everybody seems to think. We don’t need to code depths as complex as we all seem to think either. I would imagine it would be very similar to the PT boat. All we need at the moment is the
illusion of under water and above water. If you’re under water there’s no need to code ocean environment because you would be in the control room and using your sonar and clipboard for reference. NO F3 when under water!!! When you see on your gauges that you’re close to the surface you may use your periscope witch would be like using a gv sight, though your sub is visible there’s no icon. Icons would appear when you are finally above water and you are also able to use f3. Much like the gunner positions on a bomber until you’re in the air, you are unable to use your deck guns until you have fully surfaced. The deeper your sub is the less likely it will be sunk by anti sub weapons. Should you exploit you oxygen or your batteries you will automatically lose your engines and surface to await your death or ditch. One thing I have yet to know of yet, is it possible to code depths in the game and how land masses affect them? <--- feedback on that
Here, a rough example chart I made. Put the Crush depth level where ever youd like on it.

feedback, opinions, addons, constuctive critisism, all welcome. Just my 0.02$