Isthmus - It is a narrow strip of land that connects two landmasses and separate two bodies of water. Island is any piece of sub-continental land that is surrounded by water. Islands may be classified as either continental or oceanic. Islands may occur in oceans, seas, lakes or rivers. Bay: It is a body of water partially surrounded by land. It is generally smaller and less enclosed than a gulf. A bay has an inward land curve. Strait : It is a narrow passage of water connecting two large water bodies e.g., seas and oceans.