The Mermaids can place a town marker in the middle of a river. Does this block the shipping routes of other players? Seems to me that it should but that may give Mermaids an unintended weapon.
I'm working toward a solo version which I will describe when I'm sure it works. Have to have at least 14 play tests though so it is taking some time. I LIKE a game with this many ways/factions from which to approach it.