November 01, 2010
More Thoughts About Diving the Cold Waters of the California Coast
Sometimes seasoned divers forget what it’s like to be a new or relatively new diver. It takes diving in a new environment to understand what new divers are going through. Sometimes even the slightest change in your usual diving pattern can bring you to a startling realization that you are not always within your comfort zone.
If you’re used to diving the warm waters of the Caribbean and you plan a trip to go diving off the Pacific coast, you might want to consider making a few dives in a lake or quarry where the visibility isn’t perfect and the temperatures are colder to acclimate some before you go.
I have made probably 1000+ dives in rock quarries, lakes and rivers in Tennessee where the mean temperature is 55 degrees. What this means is that the water is colder than it is in Florida, and certainly in the Caribbean!
I remember taking students to the quarry for evaluation dives and they’d be wearing 5mm or 7mm wetsuits, hoods, and gloves and they’d be comfortable down to about 40 feet. During the last evaluation dive we’d swim out across the deep section to get over where the paddlefish hang out and occasionally students would ask, “Are we going to go deep or stay fairly shallow?” My reply would always be, “We’ll stay in your comfort zone for now, and that will be 40 feet or shallower.”
Inevitably, one or two students would say, “Well, I want to go to the bottom of the quarry! I want to go deep!” I’d smile and say, “We’ll see. C’mon, let’s go.” Without fear, I’d know that my students wouldn’t be able to bear the cold waters that lurked below. One of my wonderful dive masters would lead the way and I’d bring up the rear so I could keep an eye on everyone. Sure enough, I’d see that headstrong student go a few feet deeper than their classmates, dipping below the thermocline, but immediately come back up and join the crowd.
Once the dive was over, that depth-defying student would proclaim, “Man! It’s COLD down there!!” They’d remember what a thermocline was from the environment lecture, but they’d never forget how the first time they experienced one felt.
The thing about diving where there are drastic thermoclines and cold water is that, like it or not, you will use more air. It’s not that you want to, but you do because your body is trying hard to generate heat. Unfortunately, as we breathe cool, compressed, dry air, we are actually cooling our bodies down even more.
Air management simply must be considered when diving in cold water. Period. We went to San Diego a few weeks ago to dive Islas Coronado, the Yukon, the Ruby E, and the NOSC Tower. The water was a fair bit warmer down around Islas Coronado, so I actually skipped wearing a hood during our second dive there. We were only going 20 feet or so to hang out with the sealions, but even so, I still got a little chilled by the end of the hour-long dive.
The rest of our dives were considerably colder, so I wore my 6.5mm wetsuit, thick hood and gloves. I considered taking my drysuit, but since Conrad was diving wet, I decided to be nice and do the same. It really wouldn’t have done me much good to wear mine, since he tends to get cold quicker than I do, plus our air supply had to be considered, as well.
When diving in the Caribbean, it’s easy to have 45 – 60 minute dives with a maximum depth between 80 – 100 feet and still come up with air left over. Wall and reef diving is most often multi-level diving where we start off at our deepest depth and gradually come up shallower so we are on-gassing less nitrogen and using less air than if we were diving a square profile, as is often the case when wreck diving. It’s easy to be relaxed and breathe slowly and methodically when diving in warm water, so air consumption is always better in these conditions.
In cold water wreck diving it’s more common to have dives 30 – 40 minutes in length with not much air remaining in your tank at the end of the dive. As I said earlier your body is working harder to stay warm. Without heat our bodies begin to shiver. Once you start shivering, it’s time to end the dive. Period. Your core temperature has dropped and it’s only going to get worse from there. Air consumption suffers greatly when shivering begins, too.
The risk of hypothermia increases when diving in cold water, or even when diving in improper exposure wear in warmer water. If you feel cold or are shivering, or are planning on doing more diving, the best things you can do is dive reasonably, come up if you start shivering, add extra thermal protection, drink and eat warm nourishing foods and beverages, put on warm clothes between dives, and get in the sun to warm up.
Some people believe your tolerance can build up with practice. I believe there is some amount of truth to that theory, because I know the more frequently I dive in cold water, the more used to it I become. Perhaps it’s psychological, or perhaps my body actually is becoming more accustomed to the colder water. Perhaps it’s simply that my body is becoming familiar with how the cold water feels as it fills my wetsuit, but whatever the reason, I do enjoy cold water diving.
I’ve just become accustomed to the fact that I need to have warm clothes available for between dives and afterwards, I need to eat soup and have hot chocolate or tea while on the dive boat, if it’s available, and I need to end my dive if I start feeling too cold. I have also gotten used to the idea that my air supply will not last quite as long in colder water as it does in warm water. But you know what? It’s well worth it! All the creatures that are found in these waters are amazing to see. Where else can you spend an hour in the water with sealions parading around and frolicking in front of you?
Eventually, I will pull my drysuit out and wear it during these types of dives, but for now, I’m enjoying the experiences and sensations of the cold waters of the Pacific.