large gulf of the Baltic Sea, bounded by the northern coast of Latvia and the western coast of Estonia, about 7,000 sq mi (18,000 sq km) in area. The gulf is separated from the Baltic Sea proper by Estonia's Muhu archipelago, but navigation is possible through several straits. The gulf, icebound from December until April, has a maximum depth of 177 ft (54 m). The coasts are mostly low and sandy, and several important rivers, including the Western Dvina, reach the sea there. There are several ports and resorts on the shores of the gulf, particularly Riga itself.