If you spend enough time around the ocean, you start to feel its natural rhythms. In San Carlos, we rely on the predictable, seasonal swings of the Sea of Cortez—the crisp, nutrient-rich winters and the warm, action-packed summers. But every few years, the Pacific Ocean decides to flip the script. It sends a massive pulse of warm water toward the Americas, changing weather and ocean currents on a global scale. This is El Niño.
For scuba divers, an El Niño event completely transforms the underwater landscape of the Gulf of California. It alters the temperature, the visibility, and the cast of characters on the reef. If you are planning a trip during an El Niño cycle, here is exactly what you can expect when you giant-stride into the water.
The Thermostat Breaks: Bath-Warm Water
The most immediate and noticeable effect of El Niño is the temperature. During a strong event, the unusually warm equatorial waters push northward into the Sea of Cortez.
Normally, our deep waters stay relatively cool, creating distinct thermoclines. During El Niño, that warm water pushes deep down into the water column. You might descend 80 feet down the wall of Isla San Pedro Nalasco and never hit a cold patch. For divers who hate being cold, this is a dream come true. You can often dive deep into the winter months wearing a 3 or 5mm wetsuit, enjoying incredibly comfortable, tropical-feeling water.
The Visibility Boom (Goodbye, Green Soup)
The Sea of Cortez is famous for its “green soup”—the massive plankton blooms that form the base of our incredible food chain. However, plankton thrives on cold, nutrient-rich water upwelling from the deep abyss. Because El Niño acts like a thick, warm blanket on the surface, it prevents that cold water from rising.
The Result: The plankton dies off. While this temporary dip in nutrients is tough on the local food web, it creates a spectacular silver lining for divers: unbelievable visibility.
Without the plankton clouding the water, the Sea of Cortez turns into a gin-clear, Caribbean-style aquarium. This is the absolute best time to dive the SAAS Artificial Reef. Dropping down on the 70-meter Santos minesweeper when you can see the entire ship from bow to stern in crystal-clear blue water is a breathtaking experience.
The Wildlife Shift: Tropical Vagrants and Deep Divers
Because the base of the food chain (plankton) is temporarily reduced, the marine life adapts. You won’t see as many massive bait balls of sardines, and filter-feeders like whale sharks or mobula rays might migrate elsewhere in search of denser food sources. However, this void is filled by new arrivals.
- The Tropical Invasion: The warm currents act as a highway for “tropical vagrants.” You will suddenly start seeing fish species on the San Carlos reefs that usually belong much further south, near Central America or the Galapagos. It is a fantastic time for underwater photographers to spot rare, colorful exotics.
- Pelagic Predators: Warm-water pelagic species, such as Mahi-Mahi (Dorado), Wahoo, and certain species of requiem sharks, often move closer to our offshore pinnacles, following the shifted warm-water boundaries.
- The Sea Lions Work Harder: Our resident California Sea Lions at the island don’t migrate away, but they do have to work harder. Because the schooling fish seek out cooler water, the sea lions must dive deeper to find their meals. While you will still see them playing in the shallows, they might spend a bit more time resting on the rocks to conserve energy.
Topside Changes: The Desert Blooms
El Niño doesn’t just affect the ocean; it dramatically impacts the Sonoran Desert. The warmer ocean water evaporates more quickly, feeding moisture into the atmosphere. This often results in higher humidity and unseasonal winter or spring rains in San Carlos.
While you might catch a passing shower, the reward is spectacular. The usually arid, brown desert mountains—including the iconic Tetakawi Hill—explode into vibrant, lush green. The contrast of the bright green cacti against the deep blue sea makes for some of the most beautiful topside scenery you will ever experience here.
How to Dive an El Niño Year
Diving during El Niño requires a slightly different mindset. It is less about the chaotic, nutrient-dense feeding frenzies and more about enjoying spectacular clarity and hunting for rare tropical species.
It is the perfect time to grab a wide-angle camera lens and focus on the stunning volcanic topography and the massive scale of the shipwrecks. It is also an ideal time to take the SSI Marine Ecology specialty with us. Understanding how global weather patterns directly shape the behavior of the fish on the reef makes every dive a fascinating science expedition.
The Sea of Cortez is a dynamic, living entity. El Niño is just one of its many moods—and for a scuba diver, it is a beautifully clear and comfortable mood to explore.
Ready to take advantage of the crystal-clear water? Contact us today to book a wreck dive or sign up for your SSI Marine Ecology course!