>>18865658The three lakes in Sinnoh have tiny "minilakes", made out of puddles, just north of their entrances so that you can see them before you go through. However, they have no north side, since nobody can see that far without cheats, so they end in squares at that side. It's interesting to note that they are normal puddle tiles, and you can walk around on top of them without cheats - you just can't get there without them.
You can see the bottom portion of mini!Acuity in this image.