Dear Nadia:
You're confused and, as a consumer, you have the right to be.
However, I noticed that someone else is mighty confused! That salesman that told you not to use travertine in a wet environment!
Travertine is one of the most suitable stones for wet environments
Of course, to minimize the maintenance issues, you will want to have it either hone-finished or tumble-finished. Higly polished is not the best choice.
But if you choose the stone wisely and - more importantly - have it installed right, you will enjoy your travertine for many years to come!
The key is the installation. I've seen all too many shower stalls that needed ripping out because of faulty installations. But that does not apply to stone only; even ceamic tiles are not free of the same problems if the installation is faulty!
To find out how to intall a shower stall properly, you can get the Mintenance Guidelines about Residential Stone Installations that's available in pay-per-download format in the Literature section of our website at:
http://www.marblecleaning.org/literature.htm.
And remember,
every single penny of the cost of the literature will be used to support this nonprofit site and its mission.
It may seem odd that you can find important installation tips in guidelines about maintenance, but the fact is that maintenance never starts after the cutting of the ribbon. Whatever is done before that: the selection of the stone and its installation have a huge bearing on the future maintenance. Hence, in the chapter of the guidelines aout shower enclosures you wll find important tips on installation, as well as maintenance.