1) Since you meet submariners from other countries occasionally and talk through your own groups, chats, etc. - you are all considered friends right? But once in the water when carrying out missions, each crew other would consider each other as enemies? Don't communicate with one another to try to find out and say, hey remember me - we meet last time or are in the same chat group or something like that?

2) Does alarm ringing, playing music loudly, shouting or screaming in the sub will cause it to be discovered? I know knocking on metal walls and pipes probably would.

3) Does anyone suffer mental distress during long missions? Especially those who are claustrophobic or uncomfortable of closed spaces, but then again probably they would test this before selecting the crew.

Do you encounter underwater turbulence when sailing through typhoon, storm, tsunami or earthquake? Probably the effect would be greater if you are closer to the surface, or can dive deep enough to not feel the effect?