Greek authorities say they are searching for the captain of a small Polish-flagged sailboat found moored in a bay on the island of Salamina, near the country’s largest port of Piraeus, carrying five Syrian nationals who had been smuggled into the country from neighboring Turkey. Greece is a major entry point into the European Union for people fleeing conflict or poverty in the Middle East, Asia and Africa. The vast majority attempt the brief but often dangerous crossing from the Turkish coast to nearby Greek islands, frequently in vastly overcrowded, unseaworthy dinghies. But it is highly unus…