How to Build a Tile Bathtub: Steps to take to make a waterproof tile bathtub

I have seen  a bathtub 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 tile bathtub, but can you please advise me how to make a tile bathtub waterproof?

By Tom Kraeutler
Source URL: http://www.moneypit.com/question-and-answer/how-build-tile-bathtub-steps-take-make-waterproof-tile-bathtub