Greek authorities say smugglers ferrying migrants from Turkey to Greece’s eastern islands have in two cases adopted the new and dangerous tactic of knocking some passengers off their speedboats into the sea to avoid capture by pursuing coast guards. All eight migrants were rescued in both cases, which occurred over the weekend. The incidents come as smugglers using speedboats, instead of the flimsy inflatable dinghies with small engines they favored for years, adopt increasingly aggressive tactics to dodge coast guard patrols. According to the United Nations refugee agency, about 31,500 migrants have arrived illegally in Greece so far this year.