Waterproofing Bathtub Tile

I have seen a tub made completely of tile.  How does the tile hold water? I know that tile alone will hold water but grout won't.  I really want to make a tub like this but do you know how to make it waterproof?
Sam T., Colorado Springs, CO

You are correct that the grout will not hold water.  In this case the tile was not water proof but the material beneath the tile tub is. To build one, you would first have to construct the tub, then line it with a water proof tile membrane, then adhere the tile.  This is basically what is done when constructing a tile shower pan for a shower stall.  It's not a simple do-it-yourself project so if you really want a fancy tub, you might be better off just buying one!