The northern end of the Gulf of California in Mexico seen from Space Shuttle Endeavor. The body of water at the top of the image is the Salton Sea in the USA.

Gulfs can be created by the flooding of a low-lying strip of land by the sea. This can be the result of a rise in sea-level at continental margins like the Gulf of Carpentaria, Australia. Conversely, gulfs can be formed where the land surface is depressed or warped downward. Low-lying regions are sometimes down-dropped sections of the Earth's crust. Gulfs which occupy such tectonic depressions include the Gulf of California and the Persian Gulf.

Where a gulf is very enclosed a strait may link it to the ocean or sea, for example the Persian Gulf linked to the Gulf of Oman and the Arabian Sea by the strait of Hormuz.

Gulf shape and configuration depends on topography. Along rugged coastlines gulfs can have very complex shapes, connect with more than one strait as well as other gulfs and feature islands. One such coastline is the southern coast of Chile where the Andes mountain chain extends into the sea and there is no coastal plain. Its crinkled pattern contrasts with the sweeping bays and curving gulfs of the Argentine coast.