Manic Digger

Been having a blast in Manic Digger.

It's an open source clone of Minecraft.  One of the cool features is seasons; in the winter, the top layer of water freezes, and you can pick up "water" blocks.

Then, you can take those blocks and drop them somewhere, and create waterfalls.

The mountain on the left has already been covered, and you can see the water starting to flow on the mountain in the distant center.

I was working in a mine when the water hit the bottom, and found myself having to fight a flood in!