ATHENS, Greece (AP) — Authorities in Greece are investigating an armed unmanned surface vessel that washed ashore on an island off the country’s western coast. A fisherman on the island of Lefkada found the craft inside a coastal cave Thursday and towed it to a nearby harbor. It was moved Friday to a naval base on the mainland for inspection, according to Greece’s public broadcaster, ERT. Ukraine has used drone boats in the Black Sea to wage an effective campaign against Russian naval vessels,