Kasonisi is a small rocky islet separated from Samos by a narrow strait. The islet is uninhabited and hasn’t any interesting features. Unless you take the local theory about a buried treasure seriously. The real attraction is the small strait with its isolated location and turquoise water.
We were taken there by a small boat and stayed for a half day. Sun lotion with high SF is essential because there is no shade to be found. Remember snorkel and mask and enjoy the water. The strait is less than 50 meters wide and with less than 1 meters depth at the most shallow part.