Decompression after a 110-foot dive: why a 5-minute stop at 15 feet matters

What is the decompression obligation after a dive to 110' for 25 minutes?

• A. No decompression required
• B. 5 minutes at 15 feet
• C. 10 minutes at 20 feet
• D. 3 minutes at the surface

Answer: (B)

After a dive to a depth of 110 feet for 25 minutes, the appropriate decompression obligation involves spending time at a shallower depth to safely off-gas the nitrogen that has accumulated in the body during the dive. The correct answer indicates that a diver should spend 5 minutes at a depth of 15 feet. This specific decompression stop allows for a controlled ascent to help prevent decompression sickness, also known as "the bends." Decompression stops are based on dive tables or dive computers that indicate how long a diver can stay at certain depths without requiring extended surface intervals to prevent nitrogen buildup in the tissues. The decision to include a decompression stop at a specific depth is essential to manage the body’s absorption and release of nitrogen effectively. At 15 feet, the surrounding pressure is lower, which aids in quicker off-gassing. This knowledge is vital for divers to ensure safety and minimize the risk of injury from improper ascent or rapid changes in pressure. By following this required decompression obligation, divers can safely complete their diving activities without significant risk to their health.

Outline (skeleton to guide the flow)

• Hook and context: a real-world scenario where decompression stops matter.

• The science in plain language: why nitrogen builds up, how off-gassing works.

• The specific example: 110 feet for 25 minutes and why the stop at 15 feet for 5 minutes is recommended.

• How these stops are decided: dive tables vs dive computers, residual nitrogen time.

• Practical how-to: what to do during the stop, common mistakes to avoid.

• Quick myths and real-world tips: safety, buoyancy, and pacing your ascent.

• Wrap-up: the big picture—why following stops protects you and keeps adventures going.

Article: Decompression stops explained with a real-world feel

Let’s talk through a scenario that’s surprisingly common among divers who push a bit deeper and a bit longer. Picture this: you’ve planned a dive to 110 feet, and you’re down there for about 25 minutes. It’s a pretty typical recreational depth if you’re chasing bigger wrecks or exploring a promising ledge. Then you start your ascent, and you’re reminded that the ocean isn’t giving away its air just because you want to finish a thrill run quickly. After that long bottom time, the right decompression obligation is a short pause at a shallower depth—specifically, 5 minutes at 15 feet. That’s the official answer you’ll see in most sets of dive guidance for this scenario, and it’s there to keep you safe.

Let me explain the core idea behind decompression stops. When you go down deep and stay there for a while, your body doesn’t fill with nitrogen uniformly like a single sponge. Different tissues soak up nitrogen at different rates. Some tissues soak it up quickly; others take longer. As you stay deeper, more nitrogen dissolves into those tissues. When you begin your ascent, the pressure is released, and you’ve got to give the dissolved nitrogen time to come out of solution slowly. If you hurry to the surface, those dissolved nitrogen levels can form tiny bubbles in your tissues and bloodstream. That’s what we call decompression sickness, or DCS—the bends—and it’s exactly what decompression stops are designed to prevent.

Now, why does the instruction say 5 minutes at 15 feet after a dive to 110 feet for 25 minutes? Here’s the practical reason. A stop at 15 feet (about 4.5 meters) is shallow enough that the ambient pressure isn’t dramatically higher than surface pressure, but it’s still higher than the surface. Being at 15 feet gives your body a controlled, gradual off-gassing path. It’s a gentle ladder back to the surface, not a sprint up a cliff. That five-minute pause lets the nitrogen that’s saturated in your tissues begin to leave safely, reducing the risk of bubble formation once you finally reach the air at the surface.

Decisions behind the scenes: tables, computers, and why numbers matter

You might wonder how a single number—five minutes at 15 feet—gets decided. The method behind it comes down to two main tools: dive tables and dive computers. Both are built to estimate how nitrogen moves in and out of your tissues during and after a dive.

• Dive tables: Think of tables as a map. They lay out depth and bottom time, then tell you how long you should wait before surfacing, or what depth and time you’ll have for a decompression stop. The math is complex, but the result is a clear set of steps to stay within safe limits.

• Dive computers: A computer is a tiny, smart assistant that uses algorithms to track your depth, your rate of descent and ascent, your overall time underwater, and sometimes even your breathing gas mix. It updates in real time, and for many dives it can tell you whether you’re inside or outside a no-decompression limit. In our scenario, the computer may show a similar stop requirement, or adjust the number slightly based on your actual ascent profile, breathing rate, and any safety margins it applies.

The key message is this: your decompression obligation isn’t a random number. It’s the safety mechanism that matches the physics of pressure change to your body’s nitrogen dynamics. Whether you’re following a table or a computer readout, the goal is the same—gradual off-gassing to prevent bubbles from forming as you come back to surface pressure.

What to actually do during the stop (and why it matters)

During a 5-minute stop at 15 feet, you’ll want to stay neutral and relaxed. Here are some practical tips:

• Hold your depth consistently at 15 feet. Avoid drifting up or down; a stable position is easier on the body and the buoyancy is more predictable.

• Keep your breathing steady. Don’t hold your breath or over-exert yourself. Slow, regular breaths help with gas exchange and reduce strain.

• Monitor your time. Five minutes goes by faster than you think when you’re watching the gauge or computer. Don’t rush the last 30 seconds—count them, but don’t overfeel the timer.

• Stay with your buddy if you’re diving with one. There's safety in numbers, and a partner can help notice subtle signs of trouble you might miss in the moment.

• Manage buoyancy. It’s easy to overcorrect when you’re subtly adjusting your position. Small, deliberate movements keep you at a stable depth without fighting the system.

If you’re curious about the science-y side for a moment, here’s a helpful analogy: imagine your nitrogen—loaded at depth—as sugar soaking into a sponge. At deeper depths, the sponge becomes “sweet” faster. As you ascend, you don’t want to squeeze the sponge too quickly—so five minutes at a shallower depth helps the sugar dissolve slowly, evenly, and safely.

Common questions and how the real world handles them

• What if the stop isn’t convenient in the moment? The rule is safety first. If something disrupts your planned stop—like a strong current or an equipment issue—abort the ascent in a controlled way and re-establish a safe profile. Your instructor or supervisor would emphasize following the most conservative option to protect you.

• Can I shorten or skip stops if I feel fine? No. Feeling fine is not a reliable indicator of decompression health. DCS symptoms can be delayed and insidious. The stops are part of the protective routine you’ve trained for.

• Do computers ever give different numbers than tables? They can, because computers adapt to your actual dive profile. That means a stop might be a few minutes longer or shorter depending on your ascent rate, depth fluctuations, or the algorithm’s safety margins. The core idea remains: don’t rush to the surface.

• Are decompression stops only for big, deep dives? They’re most common in deeper or longer-profile dives, but complex profiles can appear anywhere. Even moderate depths sometimes require short pauses if the nitrogen load is high enough.

A few more practical pointers from the field

• Buoyancy control is your best friend. Consistent depth during the stop minimizes stress on your body and makes the stop more predictable. If you’re constantly fighting your buoyancy, you’re using energy you don’t need to spend—and that can complicate an already careful phase of the dive.

• Keep an eye on your gas supply. Decompression stops aren’t clickable add-ons; they’re part of the journey. Make sure you’ve allocated enough gas to handle the stop and a safe ascent, plus a margin for contingencies.

• Respect the process. It’s tempting to rush through the surface portion, especially on a calm day. But that final phase is when your body finishes off-gassing. Slowing down reduces risk and preserves your future diving experiences.

The human side of the science

Underneath the numbers and the gear, decompression is really about respect—respect for the pressure and the way your body handles it, and respect for the ocean that holds you. The 5-minute pause at 15 feet isn’t a random rule; it’s a careful balance between time spent underwater and the safety of your body’s tissues as pressure returns toward the surface. When you’ve planned a deep, longer profile, that pause is your friend, not a nuisance.

Closing thought: staying curious, staying safe

So, in our scenario, after a 110-foot, 25-minute outing, the recommended decompression obligation is a five-minute stay at 15 feet. It’s a small window, but it packs a big safety punch. With the right planning, calm execution, and a healthy respect for the physics of pressure, you can keep exploring with confidence. The water calls to us in that timeless way—offering beauty, quiet, and a humbling reminder that even in a sport built on precision, the sea still holds the pace.

If you’re ever unsure, lean on your training, check your instrument, and communicate with your buddy. Those habits aren’t just rote steps; they’re the quiet foundations of safe, enjoyable underwater adventures. The ocean isn’t going anywhere, and with thoughtful decompression practice, you’ll be back to share another story in the world above the waves.

Takeaway: after a deep, longer bottom time, a careful pause at a shallower depth—for a precise duration—is how we breathe easy back to the surface. In this case, five minutes at 15 feet does the job, letting your body off-gas nitrogen in a controlled, safe way. And that’s the magic of combining science with a calm, patient ascent—so you can keep exploring, safely, another day.