Milly, There is an Associatioi that you might want to look up. It's the "American Association for Nude Recreation". There is a lot of information about the nudist lifestyle, and covers a lot of the laws. As was mentioned earlier, there are ussualy no laws against nudity. There are laws against "Indecent Exposure" ie a flasher.
I live in the Delta Area here in Calif., and there are actually a couple of tour boats catering to nude recreation. I really like your comment that you are not worried about being seen, but don't want to offend. That pretty much sums up most peoples attitudes.
In last years Ba HaHa Rally, one crew vowed to sail the entire Rally nude, and was succesfull.
Out on a boat, it's your world. Look around at boats around you, and without binoculars or telescopes, how much of them can you make out. They have the same view of you that you do of them. They might be able to see that you are nude, but they aren't seeing private parts.
I have a public park near by that I hike and ride my bike nude in. The Rangers know me, and have told me that it was no problem, unless someone actually ask's me to cover up.