This islet in Laganas Bay in the south of Zakythos is often called Turtle Island, as it’s a hatching ground for the loggerhead sea turtle.
For that reason Marathonisi is uninhabited and visitors have to clear the sandy beach to the north before sunset in summer to allow the turtles to come ashore to lay their eggs.
At the southern harbours of Limni Keriou and Laganas you can embark on turtle-spotting cruises to the island, normally on a glass-bottom boat.