A speedboat has collided with a tourist vessel off the Greek Island Aegina, near Athens, leaving at least four people dead including a child.
The crash also left several people injured, a nearby coastguard has reported.
The captain of the tourist boat was pronounced dead at the scene and eyewitnesses have reported seeing the boat split in half upon impact.
Twenty one people were rescued from the waters as the tourist boat sank, and a search and rescue operation including speedboats, helicopters and private boats is continuing to look for further survivors.
It is believed the tourist vessel was heading towards the Greek island of Moni. Local media reports have claimed the owner of the speedboat and its two passengers are being questioned by police.