Whenever you find a normal waterfall, you can create a floating one. Basically cast raise land on both sides of the waterfall. This creates a floating waterfall.

I recommend at a future date that you make these two cliff tiles next to the waterfall not have the ability to cast the raise land spell. This should prevent the player from actually creating the waterfall. Even if you have to add special tiles to prevent this from happening about each waterfall.

I noticed that you made the raise land spell not able to raise land from the ocean floor, which prevented me from creating the floating waterfall, a big improvement to this particular problem.