This page covers information specific to Terror From The Deep. For general information on the Geoscape, please refer to the general Geoscape topic for Enemy Unknown.
The Geoscape is a combination of base management screens and the world view. The Geoscape is where you fight the strategic war, whereas the Battlescape is where you fight tactical battles. In the Geoscape, you can manage your bases, view alien activity graphs, Country Funding, view the in-game UFOpaedia, load and save games, intercept USOs, and send your aquanauts on missions. The Geoscape is played in real time, although management of bases and ordering subs pauses the game and these can be done at leisure. All non-trivial actions, such as subs flying to their destination, research, manufacturing, and so on, take time to accomplish and this time must be waited out in the world view.
The Terror From the Deep Geoscape differs greatly from Enemy Unknown in that the areas covered have been essentially inverted. Instead of land, X-Com now covers the ocean floor.
The map is basically broken into several different seas/countries. X-COM base cost will be determined by which sea it is in. Alien activity will also be specifically launched on a regional basis. Therefore, it makes sense to take this into account when placing your bases. It is impossible to place bases and to intercept USOs upon land.
Below you can see maps showing the location of the seas and the countries.