Santorini has so much to offer.
There is the 3km long Black Beach of Perissa and Perivolos and the Red and White beaches. There is a lot on offer for those who are looking for a day in the sun. All the sand is of volcanic origin and a bit rough. The black sand on the Black Beach gets real hot, so be careful.
Are you interested in archaeology and history? Visit the Archaelogical Museum in Fira. If you want beautiful views of the caldera, walk from Fira to Imerovigli (about 45 minutes). Visit magical Oia at the north tip of the island where there are magnificent sunsets and fantastic restaurants. Take a tour of the caldera on a caique (traditional Greek boat) visiting the volcano, hot springs and the island of Thirasia. Visit the old towns of Emporio, Megalochori of Pirgos. The list goes on and on. So much to do and so little time to do it.