Deep Diving
Introduction
Why go deep at all? After all, you can enjoy colorful corals and plenty of fish at just 5 meters.
Deep diving is a way to reach certain goals. People dive deep to see, do, or experience something that isn’t accessible at shallower depths.
It’s also a chance to explore new places. The Deep Diver certification opens the door to different dive sites and a range of underwater activities.
Many large, well-preserved wrecks lie at depth. Exploring them requires deep diving skills.
The deep environment allows you to encounter marine life adapted to greater depths — creatures rarely seen in shallow water.
Many drift dives happen in ocean currents that weaken or disappear in shallow areas. So deep diving is often part of current dives along walls or reefs.
This course is an exciting and important adventure that opens up the world of deep diving. It teaches the key skills needed to dive deep safely and confidently.
In this article, I’ll explain what deep diving is all about.
What Is a Deep Dive?
In recreational diving, any dive beyond 18 meters (60 feet) is considered deep — with a maximum of 40 meters (130 feet).
Although the PADI Deep Diver course allows for dives up to 40 meters, 30 meters is considered an optimal depth for most deep dives. This is due to several key factors:
Below 30 meters, you often don’t have enough time to stay within no-decompression limits, even with enriched air and a dive computer.
The risk of decompression sickness (DCS) increases with depth, as the margin for error narrows.
Around 30 meters, some divers may experience early signs of nitrogen narcosis. It doesn’t usually affect most divers at this depth, but staying shallower can help avoid the risk.
The deeper you go, the darker it gets. Even in clear water, light drops off significantly around 30 meters in temperate regions, and marine life becomes sparser. Visibility decreases and there’s less to see. In freshwater lakes, light may not even penetrate that deep at all.
Goals of Deep Diving
Before every deep dive, you should define a clear and specific purpose.
A good goal might be: inspecting a section of a wreck, photographing a particular species, exploring a coral tunnel, or doing a training exercise.
Deep dives should never be about chasing adrenaline or breaking depth records. They must be intentional and well-reasoned. Experience at depth must be built up gradually, with proper training and equipment.
Trying to beat personal records without sufficient training can be dangerous — even fatal. In diving, safety always comes first.
Safety in Deep Diving
Earning a Deep Diver certification also means taking responsibility for your own depth limits. There are five key things to assess:
Environment
Before diving, ask yourself: What’s the visibility? What’s the water temperature? Are there currents? What’s the altitude? All of this will impact your depth decisions.
Your training and condition
How many dives have you done in similar conditions? Have you dived this deep before? How do you feel today? Any health issues? These are essential questions for any dive, but especially for deep ones.
Recent dive history
Have you already done any dives today? Is your gear and dive computer ready for a dive at this depth?
Access to medical help
How far is the nearest medical facility? Where is the closest hyperbaric chamber? Emergencies are rare, but planning for them is vital.
Your buddy
What is your buddy’s level of training and experience? How are they feeling? Remember, diving is a team activity — their condition is just as important as yours.
Techniques for Deep Diving
Like any specialized area, deep diving has its own methods. These are usually advanced versions of standard scuba techniques.
Buddy contact
Losing your buddy is a serious mistake in any dive — but in deep diving, it can mean the end of the dive.
In shallow dives, you can surface and regroup. But in deep diving, limited air and short no-deco times make that impractical. Once you ascend, you likely won’t go back down.
Stay close to your buddy at all times — face each other on descent and ascent, and remain closer than you normally would on shallow dives.
Neutral buoyancy at depth
Buoyancy changes as you descend. At depth, these changes become less noticeable. That’s because gas compression slows at greater depths. I wrote more about this in my article on Atmospheric Pressure in Diving.
Head-up descent position
In deep dives, descending vertically with your head above your feet helps avoid dizziness and disorientation. It also makes equalizing easier.
Controlled descents and ascents
Rapid descents can cause ear, sinus, mask, or drysuit squeezes if you can’t equalize fast enough. Rapid ascents can make you miss a safety stop and risk DCS or lung injuries.
Monitoring ascent rate
Always follow a safe ascent rate — no faster than 18 meters (60 feet) per minute, and slower if your computer advises it.
Watch where you’re going as you ascend — look up, stay oriented.
Breathing technique at depth
Breathe slowly and deeply. This is always important, but especially so at depth.
At 30 meters, you’ll use air twice as fast as at 10 meters. If you’re working hard — say, fighting a current — you’ll burn through your air faster.
This means your tank can go from “almost full” to “getting low” very quickly. To avoid running out, check your gauge often.
Off-gassing nitrogen
A safety stop at 5 meters for 3 minutes after each dive allows your body to release excess nitrogen.
Safety stops reduce the formation of bubbles by up to five times. Models show that a three-minute stop is even more effective at reducing nitrogen load than just halving your ascent speed.
Types of Deep Dives
There are two key types of deep dives to be aware of: drift dives and wall dives.
Drift dives at depth
Drift dives are great because the current carries you — minimal effort required. But deep drift dives demand solid coordination.
Tips:
Use a dive boat: Shore-based deep drifts are rare and risky. A boat means you won’t get swept past your exit point.
Synchronized start: Start at the same time as your buddy. Don’t drift apart — there’s no time to regroup later.
Descent method: Decide as a group — deflated BCD to descend immediately, or inflated for a slower start. Currents are stronger near the surface, so unified descent keeps the group together.
Use a surface marker buoy: If allowed, trail a buoy to mark your position and help you ascend safely. Keep gear streamlined — dangling gear is dangerous and bad for the environment.
Track air and no-deco time: Monitor both carefully. No emergency air will be waiting for you at depth — leave plenty of reserve.
Wall dives at depth
Walls are beautiful — and disorienting. Follow these rules:
Depth awareness: Clear water can trick your brain. Watch your depth constantly.
Stay near the wall: It’s a good visual reference — but don’t get too close. Leave space to avoid damaging marine life.
Use the wall as an ascent reference: If the wall reaches near the surface, you can use it to do your safety stop at 5 meters.
Nitrogen Narcosis in Deep Diving
As mentioned earlier, some divers feel the effects of narcosis at around 30 meters.
Nitrogen narcosis is caused by breathing air or nitrox under pressure. Scientists used to be puzzled by this, but now we know it’s due to nitrogen being absorbed into nerve cells.
The Meyer-Overton theory suggests that all gases — even oxygen — can cause narcosis when dissolved in the fatty membranes around nerve cells. CO₂ worsens the effect, though the mechanism is still unclear.
The better a gas dissolves in fluids, the more narcotic it is. Nitrous oxide (“laughing gas”) is highly soluble and causes narcosis at surface pressure. That’s why it’s used as an anesthetic. Helium, on the other hand, is barely soluble — that’s why technical and commercial divers use helium mixes for extreme depths.
Narcosis depends on individual physiology and physical condition. Symptoms can vary from one dive to another — even for the same person.
Narcosis itself isn’t dangerous — what’s dangerous is its effect on behavior. An “intoxicated” diver may ignore depth, lose track of time, or fail to respond in an emergency.
Symptoms (what you feel):
- Slow thinking, trouble focusing
- Poor decision-making, false confidence
- Short-term memory loss
- Apathy toward safety or tasks
- Euphoria
- Drowsiness, drunk-like feeling
- Anxiety
Signs (what others see):
- Unsafe or erratic behavior
- Trouble reading gauges or understanding signals
- Ignoring safety
- Staring off into space or “zoning out”
Structure and Content of the Deep Diver Course
The Deep Diver course includes at least four open water deep dives. Students perform exercises to develop their skills for safe deep diving.
There’s also theory and a knowledge check.
A few notes on the required four dives:
- Your instructor can add more if more practice is needed.
- If you’ve completed the deep dive from the PADI Advanced Open Water course, it counts as one. Certain other certifications may also credit specific skills.
Conclusion
The Deep Diver course is an exciting journey for those who want to explore the ocean’s depths. It teaches the knowledge and skills needed to dive deep safely and confidently. Deep dives are a challenge — but one that’s well worth it when done with training, experience, and safety in mind.
This course opens doors to new underwater adventures — and reminds us to respect the ocean and its wonders. Stay curious, keep learning, and dive into discovery with confidence.