I used the Canon 24-105 f/4.0 L - versatile lens for this type of trip. Between the sand, rocking boat, and ocean mist, I wouldn't suggest changing lenses while you're out and about...
We did the Phang Nga and Phi Phi half day motor boat tours...two separate tours. Be sure to bring some plastic bags and waterproof covering for your camera!
I used the Canon 24-105 f/4.0 L - versatile lens for this type of trip. Between the sand, rocking boat, and ocean mist, I wouldn't suggest changing lenses while you're out and about...