Baja California offers several different types of marine environments for underwater exploration. The northern Pacific coast features a number of islands surrounded by rock reefs, seamounts, and kelp forests. The water here is cold (wear lots of neoprene or, preferably, a dry suit), visibility is often limited, and conditions favor advanced divers. But for those who make the trip, the marine life is fantastically unusual and diverse, and the spearfishing is excellent. La Bufadora  and the Islas Coronado  and Todos Santos  are the top dive destinations in this region.
At the other end of the spectrum, the southern Sea of Cortez along the East Cape offers tropical conditions for diving and snorkeling, with drift diving over a living coral reef, sea lion colonies, dozens of islands, secluded coves, and white-sand beaches. A few sunken ships have formed artificial reefs over the years. The most popular dive destinations in Central/Southern Baja are Loreto , La Paz , and the Los Cabos Corridor . Water temperature ranges 20–30°C (from the high 60s to the 80s°F), and visibility often exceeds 30 meters (100 ft.). July–October is the best time to go.
Baja’s only dive shops are located in Ensenada , Mulegé , Loreto , La Paz , Buena Vista  (East Cape), Cabo Pulmo  (East Cape), San José del Cabo , and Cabo San Lucas . Most of these shops offer guided dive and snorkel tours, rental gear, and lessons. Note: When diving in the protected marine parks near Cabo Pulmo, Loreto, and Cabo San Lucas, diving with a guide is required by law. For this reason, the shops in Cabo Pulmo do not offer airfills to independent divers.
The Solmar V (www.solmarv.com , tel. 866/591-4906) and the Nautilus Explorer (www.nautilusexplorer.com , tel. 888/434-8322) both offer liveaboard diving, to the Socorro Islands, Guadalupe Island, and Sea of Cortez, among other trips.
Scuba gear is hard to buy in Baja, even in the resort areas. Bring your own or plan to rent. On that note, it’s a good idea to bring your own spare parts kit and safety equipment, even when diving with a guide. You don’t want to sit out a dive when your mask strap breaks or the O-ring on your tank blows. Likewise, a safety sausage, whistle, and dive knife are must-have accessories.
Cabo San Lucas (Buceo Medico Mexicano, Plaza Marina, tel. 624/143-3666, cabo [at] sssnetwork [dot] com), La Paz (Baja Diving and Service, tel. 612/122-7010, www.clubcantamar.com ), and Playas de Tijuana (Centro Hosp. Internacional Pacífico, CHIP, tel. 664/685-2566) have the only recompression chambers on the peninsula. In San Diego, head to the Hyperbaric Medicine Center at the University of California Medical Center in San Diego (U.S. tel. 619/543-6222, 7:30 A.M.–4:30 P.M. Mon.–Fri. and for emergencies).