The Bzg

A waterloggable Block, e.g. a fence or a half slab is being waterlogged by two adjacent water source blocks

How to reproduce

build a 5x3x1 plate of solid blocks, break the middle 3 ones. Place a waterloggable block in the middle and will the left and right air blocks with a water source. 

It will waterlog the waterloggable block, creating an infinite water source. 

Expected result

The waterloggable block should not get waterlogged

Actual result

The waterloggable block gets waterlogged