[bb88]

Hmmm... That seems like a valid move needs to exist for all possibilities for every square.

Water should probably be allowed to hit over too, but not in.

[stevage]

how do you hit over water in mini-golf?

[theOGognf]

By hitting it sufficiently hard

[bb88]

There are videos of people skipping balls off the surface of water.

https://www.youtube.com/watch?v=bcI9nzsCILI

[stevage]

Yes, but that's not mini-golf.

Also I don't think the ball in that video is skipping, it's bouncing off a rock. Definitely possible to skip though.