Yes, each tile is two bytes, one for the actual tile type and one for the water level. The water level byte is a number between 0 and 6, where 6 is completely filled with water. It's also used as the offset from the beginning of the sprite [000000000000FCFCFCFCFCFC] when I update the back (water) every frame. Notice a water level of 6 gives you [FCFCFCFCFCFCXX], 5 gives you [00FCFCFCFCFC], and so on:

+0 ░░ ░░ ░░ ░░ ░░ ░░ ░░ ░░ ⎫
+1 ░░ ░░ ░░ ░░ ░░ ░░ ░░ ░░ ⎬ level 0
+2 ░░ ░░ ░░ ░░ ░░ ░░ ░░ ░░ ⎪
+3 ░░ ░░ ░░ ░░ ░░ ░░ ░░ ░░ ⎪ ⎫
+4 ░░ ░░ ░░ ░░ ░░ ░░ ░░ ░░ ⎪ ⎬ level 3
+5 ░░ ░░ ░░ ░░ ░░ ░░ ░░ ░░ ⎭ ⎪
+6 ██ ██ ██ ██ ██ ██ ░░ ░░    ⎪ ⎫
+7 ██ ██ ██ ██ ██ ██ ░░ ░░    ⎪ ⎬ level 6
+8 ██ ██ ██ ██ ██ ██ ░░ ░░    ⎭ ⎪
+9 ██ ██ ██ ██ ██ ██ ░░ ░░       ⎪
+10██ ██ ██ ██ ██ ██ ░░ ░░       ⎪
+11██ ██ ██ ██ ██ ██ ░░ ░░       ⎭

The actual algorithm is a bit crude. I loop through each tile T, doing the following:

• If tile T contains two or more units of water:
  • For U = T – 1 and U = T + 1:
    • Abort if tile U's water level is higher than tile T's water level
    • Abort if the block above tile U is solid
    • Loop:
      • Abort if U + 17 is solid
      • Abort if U contains water
      • U = U + 17
    • If the water level at U is not 6:
      • Increment the water level at U
    • Else (if the water level at U is 6):
      • Increment the water level at U
    • If T is not a water pipe:
      • Decrement the water level at T
    • Draw a vertical gray line from the bottom corner of T to the bottom corner of U (flowing water); side depends on whether U started as T – 1 or T + 1
• Draw the sprite corresponding to the water level at T

(The 17s in there are because each row has 17 tiles.)

It sounds complicated, but the code for all of that (including the End statements) are just 14 lines total.

The net effect is that small horizontal segments of six pixels seem to move sideways as possible, and as far down as possible.

Notice though that this means water flows more easily to the left than to the right. I fixed that by swapping the order of I-1 every frame (one frame it starts with T – 1, the next it starts with T + 1). Yay for SMC

You lost a calulator How is that possible
And it sucks, it looked so awesome......

You've shown us screenies before, did you only transfer the executable at that time?

^ that I take care of mine like nothing else .__.

This sucks. This is why I always kept my calcs on me (in a pocket if I had cargo pants or something), not even in a pencil case. That said, I lost my Nspire Clickpad keypad once, though, but it was actually in my home.

Epic name, epic story, well deserved +1

Agreed.