By Karolina Tagaris ABOARD THE AGIOS EFSTRATIOS, Aegean Sea (Reuters) - Greek Captain Argyris Frangoulis lifts his binoculars and with eyes fixed on the Aegean Sea horizon, steers his patrol boat out near the Turkish border to a dinghy full of stranded refugees. "Everybody safe, OK?" he yells at the passengers, mainly Syrians and Afghans, approaching the coast guard vessel bewildered and in near-silence. By midday, the Agios Efstratios, a gunboat with 29-member crew who work in shifts, had plucked more than 600 people from sea and ferried them to the port of Lesbos, the island on the frontline of Europe's migration crisis.