Water-based events in SOF selection are ruthlessly effective ways to reveal the interaction between mind and body. To a much greater extent than with things like running or doing lots of pushups, you can’t solve problems in the water by just physically trying harder. You have to try better, and this is highly dependent on skill acquisition, stress inoculation, and self-regulation: brain stuff.
Much like how we instinctively feel vigilant around snakes, spiders, and men with cauliflower ears, we’re built to be highly alert to the potential danger in situations that could result in drowning.
It seems counterintuitive, but the absence of oxygen in our bloodstream doesn’t play a big role in our drive to breathe. Instead, it’s the presence of carbon dioxide. With each inhalation, we take in fresh oxygen, and then exhale CO2. That oxygen is circulated throughout our body, where it is metabolized, which produces CO2 as a byproduct.
This CO2 drives our instinct to breathe, and if it accumulates because we’re not breathing, it becomes very uncomfortable. Remember our evolutionary instincts for survival: high CO2 levels create an immediate and incredibly powerful urge to fix the situation and get out of danger.
There is almost nothing more reliably panic-inducing than suffocation or the sensation of drowning. Hypercapnic (having excess blood CO2) lab rats will go from trying to navigate the walls of a maze to smashing through the barriers if they see them as the obstacle between them and more oxygen.
This is why selection courses like to use water competency training.
It’s not really that the instructor cadre care about how good you are at splashing around in the pool, tying knots underwater, or floating on your laundry. It’s that they want to see how good you are at managing yourself under conditions that naturally create panic. Most physical events in SOF selection are ways to see into your mind, and water competency training is no different.
Yes, you need to be able to tread water and be trusted in the ocean without an inflatable rubber ducky around your waist, but the most important thing is that you’re the type of person who can stay calm, present, and thoughtful in situations that cause most people to lose their minds. If you have that, you can learn how to eggbeater tread. But the technical skills won’t matter if you can’t keep yourself together emotionally.
The harder our muscles and brain are working, the more oxygen we metabolize and the more CO2 we have to get rid of. It’s this accumulation of CO2 that drives our urge to breathe. This is why some freedivers will deliberately hyperventilate prior to their dives. They can’t increase how much oxygen their blood can carry by very much, but they can decrease how much carbon dioxide they’re starting out with, which delays their urge to breathe while underwater and helps them to stay comfortable.
The danger to this strategy is that they still need oxygen, so even if they trick their brains into thinking that they’re ok by stripping down their CO2 levels at the start of a dive, they can still become dangerously hypoxic - they just won’t be as aware that it’s happening. That hypoxia can cause a sudden loss of consciousness. This is known as shallow water blackout, and people die from it every year.
Improving your CO2 tolerance comes at a cost.
This relates to the concept of non-linearity from the beginning of our book. There are no more-is-always-better relationships in complex systems. A change in one place will influence what’s happening everywhere else.
If you’re going into a maritime SOF selection course, it’s beneficial to spend some time working on your CO2 tolerance: your ability to handle the increased carbon dioxide levels that come with prolonged breath-holds.
Remember, though, the role that carbon dioxide plays in respiration. It regulates your urge to breathe. As we covered earlier in the section on breathing, breathing does a lot more than drive gas exchange. The pressure gradients involved in respiratory cycles also play an important role in cardiac output and circulation.
The more effectively you can breathe during activities like rucks, runs, and calisthenics beatdowns, the better you’ll perform. If you’ve trained to inhibit your sensitivity to CO2 you’re going to be better at swimming 50 meters underwater, but you could conversely impair your breathing on land because you’ve taught your brain to ignore respiratory signals. You may find yourself struggling with unnecessary hypoxia or vascular occlusion during everything other than water competency activities because your subconscious drive to breathe has been suppressed.
This means four things:
- Only train CO2 tolerance to the extent that you need it. The closer you get to the margins of a physiological capacity, whether it’s maximal strength or extremely long breath-holds, the more it costs you. None of the underwater events in selection courses are at the level of a professional freediver, or even close to it. For instance, the 50-meter underwater swim in BUD/S only takes about one minute. If you can hit a 2-minute breath-hold while sitting comfortably on dry land (do not test this in the water), you’re good to go.
- If you’re in a maritime program, it’s especially important to train to consciously override the negative effects of increased CO2 tolerance by focusing on breathing. Think of the way a boxer trains to synchronize their breaths to their punches. They’re not exhaling forcefully with each punch because their subconscious mind is urging them to get more air, they’re consciously training that way in order to improve their power endurance and create a strong motor pattern. Apply the same idea to your running, rucking, and strength/calisthenics movements. Work on timing your breaths in sequence with your movements, ahead of your urge to breathe. That way you’ll stay ahead of your respiratory drive and prevent avoidable shortfalls in gas exchange and circulation.
- Treat your apnea training as mental skills practice. Whether you’re practicing water competency skills or using an apnea training app on dry land, always remember that the most important lever you have is in mental skill development and learning to regulate your stress responses. Water competency or apneic training are a direct path to panic in the brain, so approach the practice that you do around them with this in mind. You’re practicing your ability to stay calm, thoughtful, and in control in a situation acutely designed to make that difficult. They’re an excellent place to work on the mental skills described in chapter 13 of the book.
- Rather than fixating on how long you can stay uncomfortable during a breath-hold, work to increase how long you can be relaxed and comfortable. You’ll make much better progress learning to reduce your oxygen consumption and energy expenditure in the water by staying relaxed and efficient than by fighting against the reality of hypoxia. You can’t really change how much oxygen you take with you underwater, but you can change how fast you spend it.
Water competency practice: Underwater hockey
One of the best ways to improve your comfort in the water is to find a game or sport in which holding your breath, staying calm and relaxed, and moving efficiently is a means of pursuing a goal that’s inherently fun.
It’s sort of the same concept as the difference between hiking up a beautiful mountain with a pack compared to doing weighted step-ups in the gym for two hours. Despite similar mechanical demands, the hike would be enjoyable and dynamic. You’d want to move as efficiently as possible in order to cover ground with minimal fatigue and continue enjoying the process. You’d be associating the activity with a state of low emotional stress, control, and enjoyment.
In contrast, two hours of step-ups would make you want to walk into traffic. Fatigue would be a primary focus of the workout, the movement pattern would be rigid, and you’d either be distracting yourself the whole time or just waiting for it to be over.
Water competency training works the same way. It’s a lot more productive when it’s naturally enjoyable. You’ll push your body and naturally look for strategies to become more efficient because you’re inherently rewarded for doing so, not because a stopwatch and a spreadsheet tell you to. This way, you develop things like CO2 tolerance and the ability to stay relaxed under stress as a means to an end, in a real-life environment. Being good at those things means having more fun, or winning a game with your friends.
Underwater hockey is a popular form of doing this in the SOF community. It doesn’t truly resemble hockey by much, aside from a handful of mostly Europeans who literally play it with tiny hockey sticks and a weighted puck. In the SOF version, it’s played with a weighted dive brick, a rubberized weight plate, or a rubber toy torpedo that can be thrown for short distances underwater.
In any case, the goal is like most field sports in that you’re trying to get the ball/weight/torpedo across the playing area and into your opponent’s territory so that you can score a goal. This goal is often as simple as touching the weight to the wall of the pool on your opponent’s side. Some people will make what look like tiny weighted hockey goals, and you work to get the torpedo/weight into your opponent’s net.
The basic rule is that all this takes place underwater. If you’re on the surface, it’s to breathe and recover, and then you dive back down and work to move the weight across the bottom of the pool against the efforts of the opposing team.
There are many ways to work toward this end goal without specifically playing underwater hockey. Any enjoyable game or sport that puts you in the water and encourages efficiency and self-regulation is useful. Surfing, spearfishing, or bodysurfing are great options if you’re lucky enough to live near the ocean.
If you’re confined to a pool, there are plenty of games involving treading water while passing dive bricks around that can be helpful. If you’re working on swimming with fins, you can make a habit of tossing your mask and fins into the pool and then diving in and putting them on underwater at the start of your swim.
A final caveat
Be extremely cautious with any of these games, as shallow water blackout is common and can easily be fatal. Never do any sort of water comp training without a buddy who knows how to rescue you, and don’t push your limits in the water and take unnecessary risks. Specific physiological capacities like breath-holding/CO2 tolerance should be practiced safely on land, not in the water where a misstep can kill you. Spend your time in the water practicing skills, and use your dry-land training for testing and improving physiological limits.