I had a Tough 6000 with underwater housing but sold it off already to a nice gentleman.
Reason being I still prefer a Canon bcos I'm use to it.
Although it's suppose to go till 3m but i wouldn't do it for too long as the sealing at the battery/card compartment is not that tight like an underwater housing. Using in a swimming for a dip & shoot is fine. But to hold it underwater to shoot for long will be at your own risk.
As for using at Phuket to snorkel, I suggest you to get an underwater housing (abt S$350).
Because you'll be using in sea water & salt is more corrosive then chlorine. Trust me, you'll not be able to 100% rinse off all the salt unless you soak it in clean water for sometime.
Anyway, these are 2 cents worth of advise coming from someone who scuba dives.
As tough series are grade 8 water protection, the duration is unspecified or by agreement thus would have much longer duration or unspecific if within water pressure.
There are models (can't remember which brands) have duration, look at the specification. Other may limit their functions when in water but so far tough do not have functional limit unless one exceeds the depth as one diver tested the earlier Stylus series.
u can hv it underwater for 2 hrs for most of the newer ones ... more then enough as i dont think a person will be underwater 2 hrs continuously...
most can go depth of 3M .. so dont test it any deeper.
its pretty safe actually as these underwater camera are all tested by this authority call something like Japanese national standard (sort of a benchmark for all Jap stuff) .. they certified it as class XXX for underwater.. which hv different classes for different depth..