yeah, it's a nice next version idea either way!
Underwater links should feel a (somehow) constant force from the side, after all it's a river and not a lake =)
maybe if the flow would be different in different levels so that it could be either.
Also some wind would be nice so that there is some other forces to complicate things.
It's an old river arm now cut off when they straightened the river back in the 50ies. On your own levels, you can easily edit the water to be a pond or lake.