There are two major island groups known as Prince's and Marmara islands. The latter group is rich in sources of marble and gives the sea its name (marmaros is the Greek word for marble).
Propontis (Προποντίς, -ίδος) was the ancient Greek name for the sea. The name derives from pro (before) and pont- (sea): the Greeks commonly sailed through the Propontis to reach the Black Sea.
Marmara, Sea of, or Sea of Marmora, c.4,430 sq mi (11,474 sq km), NW Turkey, between Europe in the north and Asia in the south.
The Sea of Marmara, c.175 mi (280 km) long and 50 mi (80 km) wide, is connected on the east with the Black Sea through the Bosporus and on the west with the Aegean Sea (part of the Mediterranean Sea) through the Dardanelles.
In ancient times the sea was known as Propontis [Gr.,=fore-sea] from its position relative to the Black Sea.