I've realized that since the waterlog feature has been introduced to the game, that the slabs and stairs which are waterlogged have a water texture on the bottom of their texture, maybe it isn't a bug, but I  wish that it would be removed because it doesn't look nice if you bild an underwater structure and there is a water texture on the inside. 

Greatings Veadix.

What I expected to happen was...:
No water texture on the bottom side

What actually happened was...:
Water texture on the bottom side

Steps to Reproduce:
1. Place a slab or stair in the world so that you can see its bottom texture
2. Waterlog it by right clicking with a water bucket
3. See the water texture at the bottom