The Oder (or Odra) River (German: Oder, Polish/Czech: Odra) is a river in CentralEurope (mostly in Poland). It begins in the Czech Republic and flows through western Poland, later forming the northern 187 km of the border between Poland and Germany, part of the Oder-Neisse line. The river ultimately flows into the Szczecin Lagoon north of Szczecin and then with three branches (Dziwna, Swina and Peene) that empty into the Baltic Sea.
The main branch empties into the Szczecin Lagoon. The Szczecin Lagoon is bordered on the north by islands of Usedom (west) and Wolin (east). Between these two islands, there is only a narrow channel (Swina) going to the Bay of Pomerania, which forms a part of the Baltic Sea.