We have tried diving on both the west and east coasts of Mexico. There is good diving in some areas of the Baja but we have not heard of any good diving on the mainland west coast. There are dive operators but if you are an experienced diver there is not much to see. On the east coast there is good diving in a couple of areas - Cozumel for sure - and a couple places across from Cozumel on the mainland. There is also cenote diving in the Yucatan - cavern diving as opposed to cave diving - very interesting. We took our dive gear to Mexico one year but have not done it again as we were not thrilled by what we found - other than Yucatan and Cozumel. If you do go to Yucatan we recommend the operations in Akumal over those in Paa Mul - by a long shot. We have not been diving in the Baja but have heard there is some good diving there.