To seal the wall I used Redgard, then tiled over top of it - 2 coats will water proof your gympsum board. The tile board is OK but its super fragile and prone to chipping, and water damage funny enough. From my understanding it has also been discontinued, so supplys are dwindling. Spend a bit more time and do it the right way and tile.
http://www.homedepot.ca/product/redg...-gallon/921795