There isn't an unfished beach on this planet clear of plastic bottles and other marine debris washed up on it shores, but I think Eneko Island in the Marshall Islands comes pretty darn close to what I think of when I hear the word pristine.
I visited Eneko in 2007 when I attended my first Micronesians in Island Conservation retreat. The island is now exactly like it was then.
These birds are called fairy terns. Aren't they pretty?