@pastanaga - I was recently in Tonga and the manager of the resort we were staying in told us that he always had trouble with the Europeans about this sort of thing.
The Togans were quite conservative, but they didn't mind people wearing swim suits as long as they stayed in the resort area. Private land, do what you like essentially.
But there are so many nude beaches in Europe, that many of the people will just strip down entirely and go wandering around the island. He said that while the islanders were generally cheerful about swimsuits, they were completely shocked whenever they saw people completely naked in the water!
I agree that one of the best tips when you are travelling to a new culture is to read up on what is acceptable and what isn't. You never know what the differences are going to be.