Water

Water tiles are blue tiles that are unlocked in the mid-game. They usually resemble a shape of rivers or shores. Like Swamp and Mountain tiles, Water tiles require research to unlock. They are the location of Fishermen, Squid Fishers and Whaling Ports. As only the first two are available in the game, Water tiles are not crucial to one's progress.

Bridge Building
Water tiles may become extremely important once the Bridge Building research is released. This will allow resource transportation and border expansion across Water tiles.