Some years ago, I went with my best friends to Illa de Ons, a small island part of the Atlantic National Park in Galicia. There are only 2 boats per day to get there and they only allow access to a limited number of tourists per day.
As it was the end of the summer season, when we arrived we met the last group of tourists who were leaving. That meant the island was for us! And the 80 inhabitants who live there, but we only saw a couple of them during our stay.
We spent 4 days as shipwrecked on a desert island. But in a nice cabin, in which we saw every day the sunrise and sunset, and enough provisions to enjoy our time there. It was magical and very fun experience!