I count ten pairs of beady eyes curiously honing in on me, circling closer to get a better look. The raft of sea lions breaks free as a couple of inquisitive pups focus their attention on my dive buddy’s camera, currently floating loose off her arm like a buoy suspended in the water. They move in synchronisation, inspecting it closely before taking gentle, exploratory bites. Diving in the World’s Aquarium, it seems, is a two-way experience.
Photo by Kristin Paterakis
Nestled between mainland Mexico and the thin, spindly finger of Baja California, the Sea of Cortez, also known as the Gulf of California, spans roughly 1,126 kilometres from top to bottom and covers approximately 160,000 square kilometres. Once hailed as the “Aquarium of the World” by the legendary ocean explorer Jacques Cousteau, this narrow body of water is home to around 900 fish species, 90 of them endemic, as well as a third of the world’s marine mammals. It’s the type of biodiversity often associated with liveaboard trips to the most remote corners of the ocean, yet many of the region’s dive sites lie within a 90-minute boat ride from La Paz, the capital of Baja California Sur and the main access point to the southern Sea of Cortez.
Photo by Kristin Paterakis
It’s October, the start of whale shark season and the tail end of manta season. Water temperatures hover around 29°C, with calm surface conditions and excellent visibility. I spent the week diving in a 3mm Fourth Element wetsuit and stayed comfortable throughout long, relaxed profiles. It is also sea lion pup season, one of the best times to dive with some of the area’s most recognisable residents. Which is where I am now, 15 metres deep at Los Islotes, watching the sea lions watch us. Known as the Sea Lion Colony, Los Islotes is home to around 200 California sea lions and is one of the most famous dive sites in the region. Like many sites here, it is relatively shallow, but it more than lives up to its reputation. Look away from the sea lions, and you might also spot vast schools of shimmering sardines and, if you are lucky, passing pelagics cruising past.
Photo by Kristin Paterakis
Beyond its year-round residents, the Sea of Cortez functions as a migratory corridor for a wide range of marine species, and what you encounter depends largely on the season. Spring brings mobula ray aggregations numbering in the thousands, while summer and early fall offer the warmest water and the greatest overall diversity. From June through October, manta rays can be seen in the deep blue, and from October through April, whale sharks frequent the Bay of La Paz.
Photo by Kristin Paterakis
Several wrecks lie just offshore from La Paz, adding further variety to the diving. Fang Ming, a 56-metre vessel resting at a depth of 21 metres, was intentionally sunk in 1999 to form an artificial reef. Today, its rusted exterior is encrusted with coral and sponges, while inside, seagrass carpets the floor like an underwater garden. Bubbles from divers’ regulators collect against the ceiling, creating the illusion of a surface above. Morning dives are particularly striking when natural light filters through openings in the hull, illuminating the interior and revealing marine life sheltering throughout the structure, including sea lions and moray eels, while large turtles often rest on the upper deck.
Photo by Kristin Paterakis
Close by, the C-59 wreck lies at a similar depth of around 20 metres and has also developed into a thriving artificial reef. Both wrecks are accessible to newer divers, while still offering an extra level for more experienced ones through swim-throughs and limited penetration. The generally shallow depths around La Paz allow for longer bottom times, making these sites especially rewarding when diving nitrox or planning conservative profiles focused on observation rather than depth.
Photo by Kristin Paterakis
La Reina is arguably the most famous site in the region and is often considered the jewel in the crown of Sea of Cortez diving. A full-day trip from La Paz, this rocky outcrop sits farther offshore in deeper, more exposed water, where the current drives the abundance of marine life found here. Depths reach approximately 20 to 30 metres, with shallower sections for added exploration. La Reina is known for dense schools of fish and seasonal encounters with larger pelagic species, including giant Pacific manta rays.
Photo by Kristin Paterakis
On the surface, we prepared for the dive beside a solitary rocky outcrop inhabited by sea lions, mostly adult males, a bachelor colony resting after mating season. We had been warned that manta season had just ended and that the animals had already moved north along their migration route.
Photo by Kristin Paterakis
Descending, the dive is busy. Moray eels are everywhere, their heads protruding from crevices as schools of fish flutter around the reef. It is a dive spent inspecting nooks and crannies while keeping one eye on the open water. Toward the end of the dive, as we headed back to complete our safety stop, our guide began pointing urgently into the blue. A giant manta ray passed by, briefly and without warning. It disappeared almost as quickly as it arrived.
Photo by Kristin Paterakis
That’s the appeal of the Sea of Cortez: always expect the unexpected. Conditions are often calm, depths are accessible, and encounters can happen at any point in the dive. With profiles that favour time over depth and an ever-present sense of anticipation, the region rewards divers who stay alert and take things slowly.
---
Lizzie is a divemaster, freediver, and writer based in Squamish, Canada. She is a regular contributor to Original Diving, where she writes dive travel features on trends, emerging destinations, and dives worth travelling for–from the remote corners of the Banda Sea, to diving between tectonic plates in Iceland, to shark diving in Fakarava. Explore more of her work at lizzieshipley.com.
