Thanks to my brother Mike I know what bird this is. He was flying in front of the boat that took us from St. Thomas Island to St. John Island. My brother is so good that I just gave him a weak description (I had the colors backward) and he knew it was a boobie and probably a blue-booted boobie. So he got out one of his bird books and I was able to see that it was a boobie.
It was flying in front of the boat looking for fish and would dive to the side of the boat and then fly back to the front to look for more. It put on quite a show for us.
On the way back to St. Thomas it was there again.