Underwater questions [ot]

Hi,
I'm working on creating a background for a RPG set on a waterworld and I
have 
the fallowing questions:
1)  What is the maxium practical speed for under water transporation?
2)  What does a person need to live and what should be in the under sea 
comunites?
3)  Is there a detailed design system for Submarine design?
4)  Would a submarine fighter (like from Sea Quest or Archemdian
Dynasty) be 
practical?
5)  What is the best shape for a lander desgined to move though the air
and 
go into the water?
6)  What would be the best simulater for underwater combat be?
7)  Would "cralwers" be usable?
8)  What does it take to do under water mining?
9)  What would be the normal shapes that buildings be based on?
10) What type of weapons would work (lasers are out, but what about
Sonic 
weapons)?
-Stephen