San Carlos is a beachfront subdivision within the port city of Guaymas, in the northern state of Sonora in Mexico. It is noted for the exceptional clarity and warmth of the ocean water in its shallow bays. It lies on the body of water known as the Gulf of California or Sea of Cortez. There is also a very large and active diving community. There are also many Americans and Canadians that live in San Carlos during the Winter as the Summer months are very hot. There are many opportunities to fish, dive, and relax on the beach. San Carlos is a roughly 6 hour drive from the United States along Mexican interstate Highway 15 . The trip from the United States requires that you obtain a tourist visa and you are no longer required to get a car permit if you are traveling by private automobile. This is only required if you travel south of Guaymas. The area where these car permits are obtained is referred to as "El 21" as it is 21 kilometers from the border or at the border itself. Also, some of the highways in Mexico are actually tollways. As such, be prepared, cars are required to stop at checkpoints roughly every 150 kilometers to pay a nominal fee. Watch out for speed bumps. They are not always marked .