Buoyancy and Breathing: Never Hold Your Breath, Save Air and Hover Like a Pro

Rule number one: never hold your breath

When you breathe from a regulator underwater, your lungs fill with air at the pressure of the surrounding water. If you hold your breath and ascend, even a metre or two, that air expands as pressure falls and can over-inflate and rupture lung tissue. The result can be a collapsed lung or an arterial gas embolism, where air enters the bloodstream. It's one of the most serious diving injuries, and it can happen in shallow water.

Learn why this matters in why you must never dive without training.

How to breathe underwater

• Slow and deep: a full, relaxed inhale followed by a long, complete exhale. Many divers use a rhythm of roughly 4–5 seconds in, 5–6 seconds out.
• Don't "skip-breathe": deliberately pausing between breaths to save air can raise CO₂, causing headaches and breathlessness, and it's never worth it.
• Exhale fully: shallow, rapid breaths build up CO₂ and create a feeling of air hunger, which feeds anxiety.
• If you feel breathless: stop moving, hold on to something safe or your buddy, and focus on long exhales until your breathing settles.

What is buoyancy?

Buoyancy is whether you float, sink or hover:

• Positive buoyancy: you float up.
• Negative buoyancy: you sink.
• Neutral buoyancy: you hover, weightless. This is the goal for most of the dive.

Three things control your buoyancy:

1. Weights: set once before the dive.
2. BCD air: adjusted with small bursts as your depth changes. See the BCD.
3. Your lungs: a fine-tuning control. A deep breath raises you slightly, and a full exhale lowers you.

Why buoyancy keeps changing

As you descend, water pressure compresses the air in your BCD and the bubbles in your wetsuit's neoprene, so you become heavier and sink faster. As you ascend, they expand and you become lighter and rise faster. That's why you add small amounts of air as you go deeper and release air as you go up. Your tank also gets lighter as you breathe from it. An aluminium tank changes by about 2 kg over a dive.

Getting your weighting right

Most beginners carry too much weight. More lead means more air in the BCD, more drag, more effort and more air consumption. To check your weighting:

1. At the surface, with your normal gear and a tank that's close to empty (around 50 bar), fully deflate your BCD.
2. Hold a normal breath. You should float at eye level.
3. When you exhale, you should slowly start to sink.
4. Add or remove 1 kg at a time until this works. Remember that a full tank will make you slightly heavier.

Re-check when you change wetsuit, tank type or go from salt to fresh water (fresh water is less dense, so you need less weight).

Trim: dive horizontally

Trim is your body angle. A flat, horizontal position:

• Reduces drag, so you use less effort and less air
• Points your fin wash backwards, not down onto the reef or sand
• Makes it easier to hold depth and move precisely

Improve trim by moving weights (for example trim pockets near the tank), adjusting your tank height, keeping knees bent and fins up, and looking forward rather than down.

A buoyancy practice routine

• Fin pivot: lie horizontally near the sandy bottom, and use breathing alone to raise and lower your body.
• Hover: hold still at a fixed depth for 30–60 seconds without moving your hands or fins.
• Ring or marker drills: swim through hoops or hold position next to a marker at your safety stop.

The Peak Performance Buoyancy specialty is excellent value.

How to use less air

1. Relax. Anxiety is the biggest air thief. Experience fixes most of it.
2. Move slowly, with long gentle fin kicks, and keep your arms still (fold them or hold them in front of you).
3. Stay warm. Cold divers burn more air. See wetsuits.
4. Get your weighting and trim right.
5. Streamline: clip hoses and gauges, no dangling equipment.
6. Stay shallower when you can. Air use rises with depth.
7. Fix small leaks, like a bubbling O-ring or inflator.
8. Dive more. Air consumption improves naturally with experience.

Frequently asked questions

Why should you never hold your breath while scuba diving?

Because air in your lungs expands as you ascend. If you hold your breath, it can over-expand and damage your lungs, sometimes causing a life-threatening gas embolism, even in shallow water.

How can I stop sinking and floating during a dive?

Use small BCD adjustments and wait a few seconds for them to take effect, fine-tune with your breathing, check you're not overweighted, and keep a horizontal position.

How much weight do I need for scuba diving?

It varies with your body, wetsuit, tank and water type. Do a surface weight check: with an empty BCD and a normal breath you should float at eye level and sink slowly as you exhale.