A 7-year-old boy who suffered serious head injuries off the coast of Zakynthos when he was hit by a speedboat last Saturday, was said to be in stable condition on Thursday.
The boy underwent neurosurgery on Sunday and remains in critical condition at the Patra University Hospital in western Greece.
Doctors said he had stabilized on Thursday and that Friday could be decisive.
The three people who had been aboard the boat which hit the boy were arrested. The exact circumstances of the accident were unclear.