The coldest currents in living memory have chilled Pacific dive sites these past few weeks. The cold, green-water thermoclines lying below warmer surface waters looked like pea soup and felt like a windy day on the top of chilly Chirripó, Costa Rica’s highest peak. This cooling of the eastern tropical Pacific is known as La Niña, and this was the strongest one in memory for everyone with whom I have spoken.
This “Little Girl” has been so strong that she caused heavy rains all over the country in the middle of the dry season. When the warm tropical breezes blew over the cool waters, the air was cooled and forced to give up water, just as if it were rising over mountains.
Sea surface temperatures dipped into the high 70s, and the thermoclines below reached as low as 64 degrees at only 40 feet deep.
These kinds of conditions are unknown in the history of sport diving in Costa Rica.
On some days at certain Pacific sites, the cold thermoclines have reached all the way to the surface, chilling even snorkelers and surfers.
Divers have been putting on every scrap of wetsuit that can be found. Unfortunately, few dive operations here are prepared for such cold conditions, and divers are coming back chilled for the rest of the day despite the hot tropical sun.
The upside to all the cold waters is that they are more productive than warmer waters, meaning they support more life. The cold waters are full of tiny plankton, which in turn attract plenty of big stuff. The ocean seems to be wall-to-wall with marine life.
Schools of fish cover hectares. One pod of thousands of dolphins I joined last week off southwestern Costa Rica’s OsaPeninsula covered more than 10 kilometers of ocean.
Pacific offshore dive conditions have been much better than at any other dive sites during the cold waters.When the water is a couple of thousand feet deep, the thermoclines drop a little lower, leaving a clear blue layer of warmer water on the surface. Visibility in the first 20 or 30 feet of water has been a hundred feet or better, perfect for diving with sailfish, turtles, big sharks, manta rays and more. But if you dropped down below the thermocline, visibility dropped to five or 10 feet and the temperature became unbearable. Luckily, these conditions often concentrate the marine life just above the cold water in the clear blue, making pelagic dive trips nonstop thrills.
The Caribbean has been reporting rain and waves, pretty much stopping diving, though conditions there and on the Pacific will probably have changed by the time you read this.
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