As far as I'm aware, the laws to carry on the water (inland) should be the same as if on land. Unless the water is a state park where you CANNOT carry per law.
Offshore, I believe you can as long as you don't leave the 'state boundries' where you permit is not valid.
I ALWAYS carry BOTH (carry/boating)on and off land/water. Not like they will get ruined. I just don't swim with my pistol on me ;-)