Marine Life

Expansive deserts and rugged mountains plunging into a blue sea may set the backdrop, but the marine life of San Carlos undoubtedly grabs the spotlight.   With one of the highest levels of species diversity in the world, there is life wherever you look and something new to see every day.   From massive manta rays to diminutive barnacle blennies, the Sea of Cortez is a rich and varied ecosystem with organisms to amaze even the most jaded travelers.

Big Stuff – Sharks and Rays, and Marine Mammals

Big animal action is what the Sea of Cortez is known for. While the waters of La Paz are best known for big animal encounters, they by no means hold a monopoly.   With rich plankton blooms resulting from deep-sea upwelling, San Carlos is a prime draw for big filter feeders like manta rays and whale sharks.

A variety of baleen whales are also seen in San Carlos, sometimes in great abundance.   The fin and Bryde’s whales are the most commonly observed, but humpbacks and even the giant blue whales are occasional visitors.     The abundance of prey also draws hammerhead sharks, dolphins and toothed whales, including orcas and sperm whales.   Sea lions reside on many offshore islands and never seem to tire of playing with divers. For more information on the large creatures of San Carlos, see our Marine Mammals and Sharks and Rays pages!


The thought of big animal encounters may be what draws travelers to the Gulf of California, but once underwater, scuba divers will be equally astounded by the abundance and variety of reef fishes. The Sea of Cortez represents tremendous diversity within its relatively confined waters.   Nearly 900 species of fishes are believed to reside within here, and approximately 10 percent of these are found nowhere else on Earth.

Among the rocky reefs, colorful Cortez and king angelfish cruise above the gaping maw of jewel and Panamic green morays.   Numerous species of gobies and blennies will hop from rock to rock.   Large schools of skipjack and yellowtail tuna are common above these reefs, as are Gulf opaleye, an endemic species.   In the small sand patches between rocks, slow down and hover for a bit and you may be able to catch the dramatic courtship displays of blue-spotted jawfish and orange throated pikeblennies as they dance above their sand burrows.   In the rubble patches and sand flats, rays are common residents, as are tiger snake eels and giant jawfish.   Overhead, dense schools of scissortail damsels and anchovies are enticements for lurking groupers and camouflaged scorpionfishes. Scuba divers and snorkelers will be consistently engaged with the non-stop action and interplay of organisms that occur along these shores.


Scuba divers and snorkelers that just “cruise” the reefs may be missing out on some of the most interesting, bizarre, and just plain weird organisms in the sea; the invertebrates. Thousands of species from many phyla exist in the Gulf of California.   Not constrained by having a backbone, they have developed into a truly stunning array of morphologies and behaviors.   From tiny copepods and other plankton upon which so many larger animals depend, to zebra ribbon worms that may stretch 25 feet/7.6m over the seafloor as they feed, there is no end to the diversity of life.

Night is an ideal time to visit these creatures.   Not only are 60% of these organisms nocturnal, but dive lights will also serve to focus attention on small patches of reef and highlight the tiny creatures that cruising divers so often miss.   Dozens of species of beautiful nudibranchs emerge at night, as do the tentacles of sun cup coral, a species that retracts during the day.   Octopuses leave their dens to hunt, and the oddly attractive sticky sea cucumbers will stretch forth their tentacular tube feet in a feathery feeding display.   Blunt-end sea hares may be observed in meter-high piles – group spawning sessions – that leave behind a basketball-sized egg mass.   Along the bottom, pieces of coral and groups of anemones appear to get up and walk away, as their hosting hermit crabs pick their way along the bottom.   With careful observation, scuba divers may only cover a few yards of reef on a night dive without ever getting bored.   The rocky jumble that characterizes much of the San Carlos bottom topography provides endless hiding places for these reclusive creatures, and consequently, opportunity for years of exploration and discovery by both scuba divers and snorkelers alike.