Slow Ascents Help Prevent Decompression Sickness During Open Water Certification

What is a commonly recognized diving illness related to rapid ascent?

• A. Decompression sickness
• B. Barotrauma
• C. Hypothermia
• D. Oxygen toxicity

Answer: (A)

Decompression sickness, often referred to as "the bends," is a diving illness that occurs when a diver ascends too rapidly after spending time at depths under water. When divers are at depth, their bodies absorb nitrogen from the air they breathe due to the increased pressure. If a diver ascends rapidly, the pressure decreases quickly, leading to a situation where nitrogen comes out of solution too quickly and forms bubbles in the body. These bubbles can lead to various symptoms, ranging from joint pain and rashes to more severe complications like paralysis or even death. In this context, barotrauma is an injury resulting from pressure changes affecting air-filled spaces in the body, such as the ears or lungs, and is not specifically related to the rate of ascent but rather to the ability to equalize pressure. Hypothermia is a condition caused by prolonged exposure to cold water and is unrelated to ascent rates. Oxygen toxicity, while a potential concern at high pressures, is typically associated with breathing excessive oxygen at depths rather than during a rapid ascent. Recognizing decompression sickness as the correct answer emphasizes the importance of ascending slowly and following dive tables or dive computer guidelines to manage nitrogen absorption safely throughout the dive.

What really happens when you rise too fast? A lot of people have heard the scary nickname “the bends,” but the science behind it is surprisingly straightforward—and something every Open Water Diver who uses SCUBA gear should know inside and out. In the world of IANTD Open Water Diver training, decompression sickness is a topic that connects gear, physiology, and smart planning. Let’s unpack it in a way that feels practical, not alarmist.

What is the illness all about?

Decompression sickness is the term many divers use for a condition that shows up when a person ascends too quickly after spending time at depth. It’s commonly called “the bends” because the symptoms often show up as joint or muscle pain. But the reality is a bit more nuanced. At depth, every breath you take contains nitrogen under higher pressure. Your body absorbs some of that nitrogen into tissues and fluids, a normal part of breathing compressed air underwater.

When you ascend slowly, the excess nitrogen leaves the body gradually through the lungs. If you shoot to the surface quickly, the pressure of the surrounding water drops fast, and nitrogen can come out of solution too quickly. Tiny nitrogen bubbles form in your blood and tissues. Those bubbles can cause pain, numbness, dizziness, rashes, or more serious problems if they affect the wrong places—like your brain, spine, or vital organs.

It’s a good reminder that the body isn’t just a bag of air under pressure; it’s a dynamic system that needs time to adjust as you change depth.

Not the same as barotrauma or hypothermia

You’ll often hear a few pressure-related terms tossed around, and it helps to keep them straight. Barotrauma is an injury caused by pressure changes affecting air-filled spaces—think ears, sinuses, and lungs—usually tied to the effort to equalize pressure rather than the rate of ascent itself. Hypothermia is about temperature: cold water draining your body heat over time. Neither of these is specifically about how fast you rise, which is why decompression illness deserves its own attention.

Oxygen toxicity is another important topic, but it’s more about breathing gases at depth than rushing toward the surface. In the context of decompression sickness, the key factor is how quickly the body loses pressure as you move upward.

Why ascent rate matters (the practical takeaway)

Here’s the simple truth: a slow, steady ascent buys you time for nitrogen to wash out of your tissues safely. The numbers you’ll see in training are meant to translate into habits you can keep in the water.

• A common guideline is to ascend at roughly 10 meters (about 30 feet) per minute. That’s fast enough to stay efficient, yet slow enough to give your body a chance to vent nitrogen gradually.

• After you’ve reached a shallow depth, a safety stop at around 5 meters (15 feet) for 3 to 5 minutes is a smart pause. This pause isn’t just bureaucratic; it’s a practical window where nitrogen can continue its controlled exit from the body.

• Always avoid holding your breath during ascent. That’s one of the oldest and most important rules in SCUBA safety because it can cause lung over-expansion injuries if air is trapped in the chest as pressure changes.

The Open Water Diver mindset isn’t about fear but about respect for a physics-driven process. You’re balancing time underwater with how your tissues handle dissolved gases. The better you understand that balance, the more confident you’ll feel when you’re in the water.

Symptoms to watch for (and what to do)

Decompression sickness isn’t a one-size-fits-all thing. Symptoms can vary, and they don’t all show up at the same moment. Early signs often include joint or muscle pain, fatigue, numbness or tingling, and a skin rash that may itch or feel prickly. Some people notice headaches, dizziness, or a sense of confusion. More serious signs—such as trouble walking, difficulty speaking, or weakness on one side of the body—require urgent medical attention.

Because symptoms can mimic other issues, the moment something feels off, stop your activity and start a safety assessment. If the symptoms are mild, you might be able to surface slowly and seek prompt medical evaluation. If anything seems severe or progressive, call for help and arrange transport to a facility with hyperbaric treatment available. Quick action saves lives.

Safety-first habits that make a real difference

You don’t have to be paranoid to stay safe—you just need a plan and the right habits.

• Plan your ascent: Don’t push for time or air depth without checking your plan and sticking to it. Use your dive computer or a reliable table to guide ascent rates and stops.

• Surface with care: If you’ve done a long or deep session, give yourself a longer surface interval before your next exposure to depth. This helps your body offload nitrogen more completely.

• Breathe, don’t hold: It sounds basic, but it’s foundational. Breath control matters just as much as gauge readings.

• Monitor your body: If you feel joint pain, fatigue that doesn’t subside, numbness, or unusual skin sensations after a session, treat it seriously. Don’t shrug it off as “just part of the sport.” Seek medical advice promptly.

• Learn the gear that helps: A good SCUBA computer, with integrated ascent rate and safety-stop prompts, is a trusted ally. Depth gauges, submersible pressure gauges, and timers also play a role in keeping your ascent disciplined. The right tools are as much a part of your safety as your skills.

Real-world tangents that matter

You’ll hear veterans talk about “stages” of a dive—short, shallow stops between longer, deeper portions. There’s a comfort in that rhythm, a pattern you can weave into your day-to-day training. Some of the most memorable learning moments come from thinking about your gas laws in the same way you think about your body’s limits: respect the math, respect the signals your body sends, and stay curious about how small changes add up over time.

When you’re practicing the Open Water Diver program, you’ll also pick up the practical habits that carry beyond the water’s edge. For example, pre-dive checks aren’t just to prove you remembered a checklist; they’re a mental warm-up that tunes you into the environment, your equipment, and your plan. The more your routine looks like a well-practiced habit, the more reliable your ascent—and your overall experience—becomes.

A word on what to do if something goes wrong

If symptoms start during or after ascending, treat it as a potential decompression issue. Get to a medical facility with hyperbaric therapy as soon as you can. Early treatment can dramatically improve outcomes. The same goes for prevention: the safer you stay through controlled ascent and no-haste surface procedures, the better your odds of avoiding issues in the first place.

The big picture: knowledge, gear, and good judgment

Decompression sickness is a reminder that the ocean is a living system, and your body responds to pressure the way a skilled instrument responds to a well-tuned instrument panel. The Open Water Diver program isn’t just about learning to breathe underwater; it’s about learning to time your movements with the physics of the environment, to trust your gauges, and to act calmly when something feels off.

If you’re someone who loves the sound of saltwater, the glow of a bright reef, and the quiet focus that comes with a slow ascent, you’ll appreciate how this knowledge threads into every underwater outing. It’s not a stack of abstract rules; it’s a practical toolkit that helps you stay healthy, curious, and connected to your surroundings.

Closing thoughts: start with the basics, then layer in practice

Knowledge about pressure, gas, and motion isn’t glamorous, but it’s incredibly empowering. It tells you why the rules exist, and it gives you the confidence to plan, execute, and recover gracefully from each underwater encounter. In the IANTD Open Water Diver pathway, you’ll build this understanding step by step—starting with simple concepts and expanding into more nuanced safety practices as your comfort and competence grow.

So, next time you gear up, remember this: slow, deliberate movements aren’t a constraint; they’re the road to a richer, safer underwater experience. You respect the depth, you respect your equipment, and you listen to your body. The result isn’t just avoiding trouble—it’s maximizing the moments of discovery you’ll carry with you after every surface interval.

If you want to keep grounding these ideas in everyday practice, start with the basics: review your ascent plan, check your gear, and commit to a calm, measured return to the surface. Those few deliberate choices can make all the difference between a routine outing and a story you tell with a smile for years to come.