If you want to sail around the entire island there is the possibility to go by fishing boat around the island. It will stop at some of the beaches and at each stop you have the opportunity for swimming, sunbathing, snorkeling and relaxing. The cave of Agios Ioannis is certainly recommended. This is the largest cave of the Cyclades and is around 15 km long. There is a whole story behind the cave and its name, and on each August 28, there is a church service in the cave. The story goes that a shepperd was taking cover under a tree because of the bad weather and fell asleep and than took off his coat and hanged it somewhere. When he came back into the village, the villagers said that there was a picture of Agios Ioannis on his coat. They then all went back to that spot where they discovered the entrance to the cave and the icon of Ioannis. Since then on each August 28 a church service is held, and the cave has the name of Saint Ioannis. The priest and all the people of Iraklia (often from other islands) go to the cave, and burn many candles.
You can walk up and down Iraklia in a few hours. There are many churches, ancient remains of pirates (Iraklia was formerly an island occupied by Pirates), a Kastro (ruins of an old fort on the hill in Livadi), mountains, valleys with olive trees, the beach of Vourkaria, the bay in Tourkopigado, many goats and sheep, and remains of third village Iraklia. The sights are clearly marked and everywhere you go you will see wooden signs to the different destinations. However, it is a tip to be made with good walking shoes or sneakers, since there are many loose stones, and on winding roads etc.