Lord Koth posted:

Underwater nations are TERRIBLE for learning the game, online play or otherwise. A lot of commonly used spells don't work underwater so you get no experience in facing or using them, movement is so limited it teaches you nothing about preparing rapid response forces, and nations on land are going to tend to ignore you in the diplomacy game because there's little you can do to affect them for a long time, and vice versa.

Aside from the few that actually can get on land vaguely effectively, water nations are mainly just for gimmicky builds and/or just setting up dickish globals that no one else can effectively respond to.