Click on the following links to learn more about r/c submarines: 

Dive System Technology
R/C Submarine Electronics
R/C Submarine Radios
What Will It Cost? 

Click here for an informative article introducing the hobby of r/c submarines. While targeted specifically at a subvet audience, its overview perspective is ideal for newbies to the hobby wanting to learn more. 

(Reproduced here with the permission of American Submariner.)