Kauai (in Hawaii) is pretty unspoiled, as is the volcano side of the Big Island of Hawaii. I was pleasantly surprised at how un-plastic those places were.
There was a thread awhile back about island getaways. Try doing a search.
We loved the British Virgin Islands (much more than the American ones.)
If you want to
really get away, look into Cape San Blas on the northwest coast of Florida. Gorgeous sugar-sand beaches.
Beautiful water and great fishing--but not a lot of amenities, though there is scuba/snorkeling. Plenty of marine life.
Here is a glimpse: