San Carlos Scuba Diving

San Carlos saw a very quiet spring break this year with families far outnumbering college students. The weather was beautiful, often in the 80’s, but it seems our winter water is clinging on for a last hurrah. Temperatures this last weekend ranged from 62-65 F. There is 70 degree water attempting to push its way north right now, and is currently about 20 miles south of San Carlos. Now it’s a waiting game, requiring sustained northerly winds to pull the warm equatorial waters into the Gulf and change the water circulation to a summer downwelling pattern.
While a tad chilly, the diving has remained excellent with visibility often exceeding 50 feet. The arrival of large jellyfish in the last few weeks has stirred some apprehension among divers, but have no fear, these are not a variety that tends to sting humans. This particular species combines plankton harvesting with photosynthesis to acquire energy, and this is an ideal time to get in the water and witness the transient bloom of these graceful cnidarians.
When warmer water arrives, they will disappear till next winter, being replaced by Physalia pacifica, the not-so-friendly Pacific Man O’ War. This is a small surface-restricted species that packs a wallop of a sting. Easily identified by its small deep blue bell that extends above the water, they are only a hazard in the top 1-1.5 feet of the water column. Scuba divers can avoid them by simply submerging, but snorkelers should be constantly vigilant if it is jelly season.
Most people crave the arrival of the warmer waters, but for those wishing to see how “the other half “lives, the next few weeks should be exciting. As the Sea of Cortez transitions to summer, the influx of deep-water nutrients slows, and photosynthesis consumes what is left. This creates a massive base for the food chain and during the next month or so, the Gulf of California will explode with organisms intent on either breeding with one another, or eating each other. Either way, it will be quite a show.

Located roughly midway down the Sea of Cortez on the western coast of Sonora, Mexico, the town of San Carlos is a top weekend destination for scuba divers from the Western U.S. A rich and varied ecosystem, the area is subject to tremendous swings in temperature, nutrient levels, and fauna between the winter and summer months.

Divers accustomed to the bright colors and crystal clear waters of the Caribbean may at first be put off by the more subdued bottom topography and variable visibility, but will soon appreciate the diversity of this region, and the sheer density of life that inhabit these waters.

When planning for a trip during the fall or spring, it is advisable to get recent information on water temperatures, as they may change substantially over a matter of a week or two. Changes in water temperatures typically lag behind changes in air temperatures by several months.

Spring, for instance will generally have settled over San Carlos quite solidly by March, with air temperatures reaching 85-95 degrees Farenheit/29.5-35C, but water temperatures will often be 62-68F/16.7-20C. During March and April, as the days grow longer and the water temperature creeps up, visibility can be highly variable, from 40-50 feet some days, to a near “pea soup” the next, as phytoplankton blooms move swell and ebb. April diving is substantially warmer than March, with waters ranging from 72-77F/22-25C, but a good 5-7mil wetsuit is still a must for most people at these temperatures

The end of May is the traditional start to the summer dive season in San Carlos.
Summer diving is outstanding. The warmer water and increased sunlight have consumed much of the dissolved nutrients, leaving crystal clear waters. A substantial base of the food chain is converted during the spring into algal biomass to feed other consumers. By June, temperatures range from 82-89F/27-32C, and will remain warm through September.

The months of October and November are transition months in the Sea of Cortez, Typically they are still relatively mild but as the circulation patterns along the Midriff Islands (near Bahia Kino) change, the arrival of sudden upwelling can bring with it a 10 degree drop in water temperatures and an associated drop in visibility over a 1-2 week period.

The arrival of these winter waters brings with them an explosion in marine life. Many of the larger billfish and tuna will depart, but the plankton draws myriad smaller creatures from the deep such as the brilliant Dall’s goby, nudibranchs, and many other species. For those equipped with a heavy wetsuit or drysuit, winter diving in San Carlos can allow scuba divers to see an entirely new mix of species that are absent from the summer dives.

Welcome to the San Carlos Scuba Diving, News and Views section of SeaSanCarlos.com. In this section we will be featuring periodic updates about the current water temperatures, visibility, and best of all, the animal sightings. We hope that our readers will find this information helpful and entertaining. We would love to hear from you if you have any comments, announcements, or dive reports you would like to share. You may post your comments in response to any of the earlier posts, or you may email us at admin@seasancarlos.com and our editor will make sure to share your announcements and reports, so long as they are within the scope of this board. Please email us if you have any suggestions about what you would like to see on SeaSanCarlos.com, or if there are improvements that you would like to see.
Cheers, SeaCortez (editor)