Between the Baja California Peninsula and mainland Mexico, the Sea of Cortez is a hidden gem of the Eastern Pacific. In this place, desert cliffs meet deep blue waters teeming with life. Celebrated by Jacques Cousteau as “the world’s aquarium,” this UNESCO-protected marine environment is home to whale sharks, sea lions, giant schooling mobulas, and humpback whales, not to mention dozens of endemic species. Diving here is all about timing — and when the conditions are right, few places offer such a diverse range of experiences and abundance in such a wild and accessible setting. Here's your complete guide to the best time to dive in the Sea of Cortez and what you'll find in each season.

Quick Summary

• Best time to dive: July to November (warmest water and best visibility)
• Water temperature: 20–30°C (68–86°F), depending on month and location
• Visibility: 15 to 30 meters (50–100 feet)
• Marine highlights: Sea lions, whale sharks, mobulas, dolphins, macro life, baitballs
• Season type: Subtropical–desert climate with summer and winter diving windows

Diving Seasons in the Sea of Cortez

Summer to Autumn (July to November)

This is the best time to dive in the Sea of Cortez, with warm, calm water and excellent visibility. From August to October, the highest biodiversity and most consistent pelagic sightings occur. Los Islotes, near La Paz, becomes a nursery for playful sea lions, while El Bajo Seamount and Las Animas attract hammerheads, mobula rays, and massive schools of fish.

September and October are also the best months for whale shark encounters in Bahía de La Paz, where juvenile individuals feed on plankton in shallow, protected bays. Liveaboards and resort-based operators capitalize on the calm seas to access offshore sites that are inaccessible during the winter. Water temperatures peak around 28–30°C, allowing for comfortable diving in a 3mm wetsuit or less.

Winter and Spring (December to May)

Winter brings cooler water, ranging from 20°C to 23°C, and sometimes choppier surface conditions. Many liveaboards shift their focus to Socorro during this time, but diving continues in areas like Cabo Pulmo, a national marine park renowned for its giant schools of jacks, groupers, and the opportunity to see bull sharks in deeper channels.

Visibility may drop slightly, but macro life, nudibranchs, and blennies become easier to spot along rock walls and coral slopes. January to March also coincides with the migration of humpback whales, orca sightings, and gray whales in the surrounding waters, particularly in Loreto and Magdalena Bay, which can be combined with dive trips.

Marine Life Highlights

The Sea of Cortez is a transitional zone — where tropical species, temperate fish, and big pelagics all collide. Year-round residents include California sea lions, green turtles, octopuses, nudibranchs, moray eels, and angelfish. But the real show begins in late summer.

From July to November, divers may encounter schools of mobula rays, baitballs chased by dorado and tuna, pods of dolphins, and even occasional orcas. Whale sharks gather near La Paz from October through early February, with sightings peaking in November and December. Hammerhead sharks are spotted at El Bajo in September and October, and bull sharks become more common in Cabo Pulmo during the winter months.

Photography Tips by Season

August to November is prime time for wide-angle photography, especially with pelagics, sea lion interactions, and big schools of fish. Los Islotes is a dream for natural light shots of sea lions, which often play with divers' bubbles and fins. Bring a fisheye lens and strong strobes for backlit reef scenes and baitballs.

During winter and early spring, drop to macro mode. The cooler water and lower visibility are ideal for capturing nudibranchs, scorpionfish, and jawfish that hide along rock ledges and coral patches. If you're photographing whales or mobulas from the surface, a snorkel setup with a fast shutter speed is ideal.

Dive Travel Tips for the Sea of Cortez

• Liveaboards vs Resorts: Both are excellent options. Liveaboards operate from July to November, often departing from La Paz or Puerto Peñasco. Resort diving is available year-round from La Paz, Loreto, and Cabo Pulmo.
• Booking in advance: For the peak pelagic season (Sept–Nov), book 4–6 months in advance, especially for liveaboards targeting El Bajo and Las Animas.
• Permits: Marine park and conservation fees apply at many dive sites (e.g., Cabo Pulmo, Los Islotes, and Bahía de La Paz). Most operators handle the paperwork for you.

Dive Operators and Itineraries

Liveaboards offer seasonal 7-night trips to El Bajo, Las Animas, Isla San Diego, and Bahía de Los Ángeles (mobula hotspot). These trips often include multiple night dives and opportunities for snorkeling with whale sharks.

Resort-based dive operators offer day trips to Los Islotes, El Bajo, and Cabo Pulmo, with flexible schedules, photo support, and Nitrox availability.

Other Top Dive Destinations by Season

If you're planning a big-animal dive itinerary in the Eastern Pacific, consider:

• Best Time to Dive in Socorro
• Best Time to Dive in Galápagos
• Best Time to Dive in Malapascua

When to Dive in the Sea of Cortez

The Sea of Cortez offers diving nearly all year, but if you're chasing manta rays, sea lions, whale sharks, and rich visibility, July to November is the sweet spot. Winter diving is calmer, quieter, and rich in macro life, offering opportunities for encounters with whales that can be observed above the surface. With dramatic marine life, volcanic topography, and a remote, wild spirit, the Sea of Cortez remains one of Mexico’s most rewarding dive destinations.