The small uninhabited island at Laganas bay, opposite Limni Keri beach, in the south part of Zakynthos is one of the places you should visit. Also known as Marathias island, Marathonisi was inhabited until WWII, has a turtle shape and is part of the National Sea Park in Zakynthos for the protection of the Caretta-Caretta turtle.
Caretta-Caretta turtles choose the sandy beach, going into the blue Ionian sea, to lay their eggs. At the edge of the pebbly coast (the second coast in Marathonisi), in the south part of the island there are two small caves. Apart from the beaches, however, Marathonisi is also renowned for its lush, virgin vegetation which will definitely impress you.
Before going to Marathonisi, make sure you have all the essentials with you as there are no shops of any kind on the island.