Cob house sinks, tubs, showers? [2 pics]

I'm planning to begin building a cob house in the next 5 or 6 years in Georgia, after I've saved enough money for construction. I've seen a lot of pictures online where they have sinks, showers and tubs made completely out of cob. I know that to seal cob you use boiled linseed oil and/or beeswax, but would this waterproof it enough to take a bath? I've heard of tadelakt, but can does it come in white? Also, could you plaster it with lime plaster before sealing it, as I'm hoping to have white walls like the beautiful Greek villas I love. Take a look at Villa Drakothea in Mykonos to see what I mean. Does anyone know how to do this, or have some ideas? I'm very interested and open to the idea of tiling my tub or shower with a pretty mosaic, but I believe it would still need to be sealed properly.