The tragic incident occurred on Sunday at a cafe-bar's pool at the resort township of Ialyssos, on the Dodecanese Island of Rhodes.
The boys went swimming in a river in northwestern Greece on Wednesday and were pulled from the water unconscious. They were later declared brain-dead.
According to local reports, police have arrested the 45-year-old owner of the establishment after it was discovered that no lifeguard was present at the time of the incident, as required by regulations
The first officer shoved the passenger off the ferry's vehicle ramp and into the sea as the vessel departed, resulting in his death.
The young teen went for a swim on Thursday afternoon at a beach in the southern Athens area of Alimos. He was declared missing by relatives and was found unconscious in the sea the same evening.
Probe into the shocking death of an 8-year-old girl, who drowned at a well-known overnight summer camp in northern Greece this past week, continues
Following the incident, the head of the summer camp, a 34-year-old, was also arrested in the early on Wednesday and brought to the Kassandra Police Department