Ferries are expected to stay docked at Greece's main ports on Friday as seafarers stage a 24-hour strike, disrupting travel to the islands.
The strike will affect the ports of Piraeus, Rafina, Lavrio, Patras, Igoumenitsa and Elefsina, as well as the Rio-Antirrio ferry crossing in western Greece.
Seafarers are demanding a 12% pay increase under collective agreements and more crew on board ships.
They also want a seven-hour working day and the designation of dangerous maritime areas, such as war zones.
Citing the risks from armed conflicts, including in the Middle East, they are calling for a doctor to be required aboard ships.
The federation representing permanent port employees has called a three-hour work stoppage from 10 a.m. to 1 p.m. the same day.
The Piraeus Labor Center will hold a 24-hour strike and a rally at 10 a.m. in the port city's Municipal Theater Square, while a sailors' union will gather earlier in the Agia Triada area.
Strikes by Greek seafarers are common and can strand thousands of travelers who rely on ferries to reach the islands.