I haven't been able to see yet but assuming Badspot did, the way the water bricks work is that they spawn a water block inside of the brick which can only be certain sizes in the first place, making the waterblock any size other then the power of two it'll automatically round of to the nearest power of 2. So if you made a 50x50 brick it'll round off to ether 32x32 or 64x64 making you fall in some parts of the brick.