Hmm, even I had a bit of trouble finding the C2 example I made of 2d minecraft-like water. Here it is:
Not the easiest to follow but basically all the water motion is done by checking the contents of grid positions around each water square.
I started with something simple like this:
If space below water is empty
then add a new water below.
To further extend it if a wall is below the water then new water is added to the left and right if the spaces are empty. Next to make areas fill up with water I treated water the same as a wall if the water had a wall to it's left, right and bottom. The water shares this info to water left and right. The final step I did was to have the water drain if walls were removed. It isn't 100% perfect but it's good enough.
Hey the capx in the topic was even in reply to RookieDev.
Is terraria water that different? I've never played it.