@Kobayashi: I did borrow (and give credit for) a number of graphics from BeBro's SubWar (it's the only good set of underwater graphics I've seen). However, Mill004 wasn't nearly as helpful graphics-wise. I borrowed graphics liberally from other sources, sometimes editing them, sometimes taking them straight.
@Arthedain: That's exactly what I was thinking. And, since water covers about 75% of the Earth's surface, there's an awful lot of places to build cities... Additionally, the layout of the terrain has created some interesting games.
@PrinceScamp: If you could, Prince, please elaborate on why "the textures don't blend".