Ha Ha!
I knew that would ruffle some feathers.
While part of that was good old ribbing and jiving, there's a reason why I said that. I started tiling pools in Phoenix back in 84 and have intimate knowledge of all things pool tile, and an indoor guy may be able to do a fine job if he is one of us conscientious setters, but even then there are things that indoor guys just don't know about. And they're set up for pools. pool scaffolding and such. You may get through it, but not like I'd do it. Same as a pool setter with no indoor experience would be. Tricks of the trade and all that you know. Plus, the pool guy should be a serious mud master, since he does nothing else but mud work underneath his tile.
Anyway, not really trying to start a feud, just saying.
Also, sounds like the OP is talking about the deck, so my point is moot anyway. Surely no one would consider travertine on the water line. specially with no grout.
TBH, travertine on a deck with no grout might be a little

too.