The basic building component is Metal. Gold can also be mined and traded with what's left of the land dwelling humans for more supplies. Fighting over these resources will play a key role, as they do in any resource gathering RTS game. The buildings are very basic, nothing new or interesting to comment on here. The variations are basically bigger, better, faster, more.
Some special subs do exist, like stealth subs and ones able to capture opponents vehicles.
There are some interesting technologies, particularly the computer hack ability that allows you to gather info on your opponent. Other than that, you basically research better armor, weapons, submarines, etc. Submarine Titans minor saving grace happens to be its environment. Strategy First has created five levels that your subs can travel through. With most torpedoes only able to fire in a straight line, the new strategy to learn is manipulating your subs depth levels as a means of defense.