Out of curiosity, why are you set on a 206 and not a R44?
The overwater safety (assuming both are fitted with floats, etc) is probably far more dependant on the pilot than the aircraft, and assuming a suitable competent pilot, about the same for either. Endurance is usually of the order of 3-ish hours for small helicopters, assuming you have the weight allowance to fill the tanks. R44s are usually cheaper than 206s.
R44 speed is slightly higher than 206 (so you get where you're going faster), but there's not much in it. You can remove doors from a R44, I assume you can from a 206 too.
I'd certainly get quotes for both, see how they compare.