Avsa Island (Avsa Adas) is a 14-square-mile Turkish island in the Marmara Sea. The island is part of the Marmara District of the Balikesir Province, in northern Turkey. The number of its visiting tourists may approach 40,000 during vital seasons. If you are coming from Istanbul, you may sail by ferry or drive by car to get to the island. Also, regular motorboats depart from Erdek and Tekirdag. Ferries from Tekirdag cost $6,46 per passenger, whereas those from Istanbul cost $8,65.