I've always thought there should be river-specific units. Longboats are a perfect one.
For this to happen, at least with the current movement and 1UPT system, rivers would need to have their own tiles (like the great wall, for example) rather than occupy the space between tiles.
I like this direction as a potential implementation, maybe expand so that all Norway units get a movement AND combat bonus in river tiles. This would be similar to Japan's Divine Wind ability, except for river tiles instead of coastal.in civ5 scenarios some civs had an UA that made their units move faster along the rivers
it could be the same for vikings (or whatever norwegian UUs are called)
My guess? when the longship presses the pillage button while at the river mouth it can choose from adjecent tiles AND tiles along the river.Yeah not sure how well a boat on land would look