The Bad Sea is a seaside settlement in southeastern Attica, built in front of the homonymous beach. It is located a little south of the Markopoulo Port. The settlement today has a population of 203 inhabitants according to the 2001 census. The beach of Kaki or Kakia Thalassa is organized, and one of the most popular in southeastern Attica. On one side there is a vertical rock that is used for climbing. A little further east of the settlement is the homonymous monastery of old calendarists. According to Greek mythology, when the barbarians attacked Greece, Zeus and Hades dragged the shores so that they could talk and left the sea water in between. As the Greeks were very few in number, Zeus and Hades helped them by asking Poseidon to send waves larger than the barbarian ships there. It has since been said that even Hades defended the Greeks. Since then, the sea in the area of Keratea has been called the Evil Sea.