A gulf is a portion of the ocean that penetrates land. Gulfs vary greatly in size, shape, and depth. They are generally larger and more deeply indented than bays. Many important trading centres are located on gulfs. Gulfs are sometimes connected to the ocean by narrow passages of water called straits. Gulfs can also have wide openings and are sometimes indistinguishable from larger bodies of water.
Example: The Gulf of Mexico, bordered by the United States, Mexico, and the island nation of Cuba, is the worlds largest gulf.
A bay is a body of water partly surrounded by land. A bay is usually smaller and less enclosed than a gulf. The mouth of the bay, where meets the ocean or lake, is typically wider than that of a gulf.
Example: The Persian Gulf is much smaller than Hudson Bay, Canada.