what is a word for many islands?

noun, plural ar·chi·pel·a·gos, ar·chi·pel·a·goes. a large group or chain of islands: the Malay Archipelago. any large body of water with many islands. the Archipelago, the Aegean Sea.

The collective noun for islands can be a sting of islands, a chain of islands, a cluster of islands, or a group of islands.