Water nations and game maps are a big pain to try and get right. As a person who makes and selects maps continually Im up against this all the time. The games logic does actually try to consider the following:
A) Nations should not be too close to each other.
B) Nations should not start out with too few neighbor provinces.
C) Land nations should not have water neighbor provinces.
D) Water nations should not have land neighbor provinces.
E) Many nations have special terrain or theme requirements (water, land, mountains, swamp, wasteland, coastal).
F) No land nation should be placed in the center of a large area of one particular terrain so that it doesnt have quick access to multiple terrain benefits in the capital.
G) And absolutely DO NOT take too much time trying to achieve A thru F
It might seem as though you have never seen that happen. And unless you play on large maps thats understandable. Some maps make it hard, some make it impossible. A map with enough provinces to allow the game to get completely thru its choice selection process without it giving up tends to be a map too large for most peoples idea of a good game. There is definitely an advantage to maps where a human has done some work on setting provinces as start, no-start, or spec-start.
And how much water is enough? If I want 10 players at 10 provs each before mandatory war, then 100 prov map MIGHT be able to place everyone well. But what if 3 water nations join? 30 water? If there is one small ocean then the D rules pushes them to the middle and too close to each other. And what if only 1 water nation joins? 1 nation with 30 provs to the land nations 10? Cries of unfair!
My favorite maps, which rarely cause me problems, are like these.
But few people want to play games that big. Maybe some of these..
but again the smaller you get, or smaller provs-to-player ratio, the less likely that everyone will be happy with the games placement of capitals unless someone hand-massages the map.
Interesting point (which I just realized myself):
When playing a solo game, Dom3 has you select the map first then the nations. But in server mode, it waits for the people to select their nations and then has you select the map. Maybe Johan was hinting.