Select the most appropriate option that can be used as a one-word substitute for the given group of words.

A sea or stretch of water having many islands

archipelago

The most appropriate option that can be used as a one-word substitute for the given group of words is archipelago.

• Harbour means a sheltered inlet of the sea, typically one providing a safe anchorage for ships.
• Ocean is a large body of salt water that covers much of the Earth's surface.
• Bay is a large inlet of the sea, larger than a cove but smaller than a gulf.

The word archipelago is the most appropriate because it specifically refers to a sea or stretch of water that is made up of many islands. The other words do not have the same connotation of being a collection of islands.