Scuba Diving Physiology
Physiology: How Diving Affects Our Bodies
Diving is an incredible adventure that takes us into a world unlike any other. But as you descend beneath the surface, your body faces unique challenges due to the increased pressure, changes in gas absorption, and the effects of temperature. Understanding how diving affects your body is essential not only for safety but also for enjoying each dive to the fullest.
In this post, we’ll explore the key physiological changes your body undergoes while diving, how to manage them, and how to ensure safe and enjoyable dives.
Pressure and Its Effects on the Body
One of the most significant factors affecting your body underwater is pressure. As you descend, the weight of the water above you increases, and for every 10 meters (33 feet) you go down, the pressure increases by one atmosphere (ATM).
Key Areas Affected by Pressure:
Ears and Sinuses: As pressure increases, the air spaces in your ears and sinuses are compressed. This is why equalizing your ears is so important during a dive. If you don’t equalize properly, the pressure can cause pain, and in extreme cases, barotrauma (damage to tissues caused by pressure changes). The same principle applies to your mask—if you don’t equalize the pressure inside it, you can experience mask squeeze, which is uncomfortable and can leave marks on your face.
How to Manage: Equalize early and often during your descent. Pinch your nose and gently blow through it (Valsalva maneuver), or try swallowing or wiggling your jaw to equalize the pressure in your ears.
Lungs: The air in your lungs is also compressed as you descend. This is why you should never hold your breath while diving—if you ascend while holding your breath, the expanding air in your lungs can cause a dangerous condition known as a lung over-expansion injury. This can lead to serious complications like pneumothorax (collapsed lung) or arterial gas embolism (air bubbles entering the bloodstream).
How to Manage: Always breathe continuously and never hold your breath. Maintain a slow, controlled ascent to allow your lungs to safely adjust to the changing pressure.
Nitrogen Absorption and Decompression Sickness
While you’re underwater, the increased pressure causes more nitrogen from the air you breathe to dissolve into your tissues. This isn’t a problem at depth, but if you ascend too quickly, the nitrogen can form bubbles in your blood and tissues, leading to decompression sickness (DCS), also known as “the bends.”
Symptoms of Decompression Sickness:
Joint and muscle pain
Dizziness or confusion
Numbness or tingling
Fatigue
How to Prevent DCS:
Ascend Slowly: One of the most important rules in diving is to ascend at a controlled rate. The recommended ascent rate is no faster than 18 meters (60 feet) per minute.
Use a Dive Computer or Dive Tables: These tools help you track your nitrogen levels and ensure you’re within safe limits. Always stick to the no-decompression limits (NDL) and take safety stops during your ascent, especially after deeper or longer dives.
Stay Hydrated: Dehydration increases the risk of DCS, so make sure to drink plenty of fluids before and after your dive.
Gas Narcosis
At depths greater than 30 meters (100 feet), the increased pressure can cause gas to have a narcotic effect, commonly known as gas narcosis. This can impair your judgment, slow your reaction time, and make you feel overly relaxed or euphoric, sometimes referred to as “the rapture of the deep.”
How to Manage gas Narcosis:
Stay Shallow: Narcosis generally isn’t an issue at recreational depths, but if you’re diving deep, be aware of the potential for it to occur.
Ascend: If you start feeling the effects of narcosis, simply ascend to a shallower depth, and the symptoms will usually go away quickly.
Oxygen Toxicity: A Concern for Deep and Technical Divers
For most recreational divers, oxygen toxicity isn’t something to worry about, but if you’re diving with enriched air (Nitrox) or going to greater depths, it becomes a concern. Oxygen toxicity occurs when the partial pressure of oxygen becomes too high, leading to symptoms like twitching, vision disturbances, or even seizures.
How to Prevent Oxygen Toxicity:
Monitor Your Oxygen Exposure: If you’re diving with Nitrox, use a dive computer to monitor your oxygen exposure and ensure you’re within safe limits.
Stick to Recommended Depths: Oxygen toxicity is more of a concern for technical divers going beyond recreational limits, but always dive within the limits of your training and equipment.
The Effects of Temperature on the Body
Water conducts heat away from your body 20 times faster than air, meaning you can get cold much faster underwater—even in relatively warm water. This heat loss can lead to hypothermia, where your body temperature drops dangerously low, affecting your ability to think and move properly.
How to Stay Warm:
Wear Appropriate Exposure Protection: The colder the water, the more protection you’ll need. In warmer waters, a thin wetsuit may be enough, but in colder conditions, a thicker wetsuit or even a drysuit is essential.
Listen to Your Body: If you start feeling cold, it’s time to end the dive. Shivering is a sign that your body is losing heat faster than it can produce it, and continuing to dive could lead to hypothermia.
Breathing: Gas Density and Work of Breathing
As you go deeper, the gas you breathe becomes denser due to the increased pressure. This means that your lungs have to work harder to breathe. At recreational depths, this isn’t usually an issue, but at greater depths, you’ll notice that it takes more effort to inhale and exhale.
How to Manage Work of Breathing:
Slow Down: At depth, take slow, deep breaths to reduce the effort required to breathe.
Conserve Energy: Move more slowly and deliberately underwater to conserve your energy and reduce your need for oxygen.
Hydration and Diving
Diving can dehydrate you faster than you might think, especially if you’re wearing a wetsuit or spending time in saltwater. Dehydration not only increases the risk of decompression sickness but can also affect your overall energy and performance during a dive.
How to Stay Hydrated:
Drink Water: Make sure to hydrate before and after your dives. Avoid alcohol or caffeine before diving, as these can contribute to dehydration.
Snack Wisely: Eating small, healthy snacks between dives can help maintain your energy levels and keep you feeling good.
Conclusion: Knowledge Is Power
Understanding how diving affects your body is a critical part of being a safe, responsible diver. By being aware of the changes your body undergoes underwater—from the effects of pressure and nitrogen absorption to staying warm and hydrated—you can prevent potential risks and fully enjoy your dives.
Every dive is a new adventure, but it's also an exercise in managing your body in an environment that’s vastly different from the surface. Keep these principles in mind, and you’ll not only improve your safety but also enhance your overall diving experience.
Stay safe, dive smart, and enjoy the underwater world!
For more tips on diving physiology and safety, check out our other resources at OSEA Divers Cozumel.
Happy diving!
