Freediving looks simple from the surface.
Take a breath, dive down, come back up.
But once I started understanding what was actually happening during a dive, I realized there is a lot more going on than just seeing how long I can hold my breath.
Pressure is increasing. Air spaces are shrinking. Buoyancy is changing. My body is conserving oxygen. Equalization becomes part of nearly every descent. And even though I may feel completely comfortable underwater, oxygen is still being used every second.
That is what makes freediving so interesting to me.
It is not just breath-holding.
It is learning how the body reacts underwater and then learning how to work with those changes instead of fighting them.
Pressure Starts Changing Immediately
One of the first things I had to understand about freediving was pressure.
The deeper I descend, the greater the surrounding water pressure becomes.
That pressure affects any air-filled space in the body, especially the middle ears, sinuses and lungs. As pressure increases, the volume of trapped gas decreases according to Boyle’s law.
The biggest proportional pressure change happens close to the surface.
At roughly 33 feet, or 10 meters, seawater adds about another atmosphere of pressure. That means the surrounding pressure is approximately twice what it was at the surface, and an air space that could freely compress would be roughly half its original volume.
That is one reason the beginning of a descent can require so much attention.
The depth number may not look impressive yet, but my body is already dealing with a significant pressure change.
Equalization Is Not Optional
My ears usually tell me about increasing pressure before anything else does.
The middle ear is an air-filled space separated from the surrounding water by the eardrum. As I descend, the pressure outside increases. If I do not add air to the middle ear through the Eustachian tubes, the pressure difference begins pushing the eardrum inward.
That quickly goes from mild pressure to pain and, if ignored, can lead to barotrauma. Trust me, as someone who had ear tubes as a child and, for some reason, never had them removed... I know all about the ear pain.
So I equalize early and often rather than waiting until my ears hurt.
That distinction matters.
Equalization should not be something I do because I am already uncomfortable. It is something I stay ahead of during the descent.
DAN notes that divers may need to equalize very frequently near the surface because the proportional change in air-space volume is greatest there.
For me, a smooth descent starts with smooth equalization.
If I am fighting my ears, forcing an equalization or trying to push through pressure, the dive is already telling me something.
My Buoyancy Changes as I Go Down
Another interesting part of freediving is that buoyancy does not stay the same throughout the dive.
At the surface, the air in my lungs adds volume and helps make me buoyant.
As I descend, increasing pressure compresses that air. Less volume means less buoyant force from those air spaces.
So the deeper I go, the less positively buoyant I generally become.
That is why a freediver may need to kick more during the beginning of a descent but then begin sinking more easily farther down.
The opposite happens during the ascent.
As pressure decreases, the compressed gas expands again and positive buoyancy increases.
It is one of those things that makes much more sense once I feel it underwater.
The water is not changing.
My relationship with it is.
The Body Has Its Own Dive Response
Freediving also triggers a physiological response humans share with other mammals.
During breath-holding and immersion, the body can slow the heart rate and reduce blood flow to parts of the arms and legs through peripheral vasoconstriction. These responses help prioritize available oxygen for organs such as the heart and brain.
This is commonly called the mammalian diving response.
It does not turn me into a dolphin.
Unfortunately.
And by no means am I a great freediver. Far from it, actually.
But it does mean the human body has built-in responses to breath-hold diving.
Research on human breath-hold divers has documented the combination of apnea, cardiovascular changes and blood-flow adjustments that occur during immersion and diving.
Understanding that changed the way I looked at relaxation.
Staying calm underwater is not just about feeling comfortable.
Unnecessary movement requires energy. Energy requires oxygen.
So kicking harder than necessary, fighting the descent or wasting movement is working against the limited oxygen supply I brought down with me.
Technique matters.
Holding My Breath Is Only Half the Equation
A beginner can easily look at freediving as a contest against the urge to breathe.
I do not think that is a very useful way to look at it.
During any breath hold, oxygen is being consumed while carbon dioxide is building up.
The urge to breathe is strongly influenced by increasing carbon dioxide, but that feeling does not provide a perfect measurement of how much usable oxygen remains.
That becomes extremely important near the end of a dive.
A diver can become dangerously hypoxic and lose consciousness, which is why blackout is one of the major risks in freediving. DAN emphasizes that many freediving blackouts occur at or very near the surface.
That also explains why hyperventilating before a dive is dangerous.
Hyperventilation can lower carbon dioxide and delay the normal urge to breathe without creating a comparable increase in the amount of oxygen available. The warning can be delayed while oxygen continues falling.
So the goal is not simply:
How long can I stay down?
A much better question is:
How controlled can I make the entire dive?
Where Spearfishing Changes the Dive
Freediving on its own is one thing. Spearfishing adds another layer.
Now I am not just managing depth, equalization, oxygen and the ascent. I am also watching fish, positioning myself, managing a speargun, paying attention to structure and trying not to let the hunt distract me from the dive itself.
That is probably where the discipline matters most for me.
A fish can make it very easy to stay a little longer, swim a little farther or convince myself I have more time than I actually do. The fish is never worth turning a controlled dive into a bad decision.
For a lot of the diving I do, freediving is what gets me down there.
Spearfishing is why I went down in the first place.
But spearfishing brings an entirely different set of decisions, risks and techniques into the dive—and that is a whole other article.
The Ascent Deserves Just as Much Attention
Getting to depth is only half the dive.
I still have to get back.
During the ascent, I am swimming while continuing to consume oxygen. At the same time, decreasing pressure causes the gases in my lungs to expand again.
The last part of the ascent is especially important because hypoxic blackout often occurs close to the surface or immediately after surfacing.
That is one reason an experienced freediver does not treat seeing the surface as the end of the dive.
The dive is not finished until I am back at the surface, breathing normally and clearly recovered.
Why I Never Treat Freediving as a Solo Activity
This is probably the most important technical point in the entire article.
I do not freedive alone. Period.
A blackout underwater can happen without the dramatic warning people imagine. If nobody is there and watching closely enough to respond, a blackout can become fatal very quickly.
Freediving safety organizations repeatedly emphasize direct buddy supervision and avoiding solo breath-hold diving. They also warn against hyperventilation before a dive.
And a buddy is not just somebody who happens to be somewhere nearby in the water.
The buddy system only works when both divers understand what they are watching for, stay in position to respond and know how to perform a rescue.
Not only that, but you and your dive partner should be equally capable of reaching the same depths. If my limit is 70 feet but my partner’s is 100 feet, then my partner needs a better-matched partner, because I’m incapable of reaching him for a third of his dive.
I know some divers and operations may be comfortable with a wider gap in depth capability, but this isn’t where I want to rely on “probably okay.” I’d rather add another layer of safety and know my partner can reach me if it ever really matters.
That is where proper freediving instruction matters.
Watching videos and reading about technique can help me understand the sport.
They cannot replace in-water training.
Technique Beats Ego
The deeper I look into freediving, the less it seems like a sport built around simply holding my breath.
Pressure management.
Equalization.
Buoyancy.
Efficient movement.
Relaxation.
Oxygen management.
Recovery.
Buddy safety.
They all matter. A lot.
Depth is just the number everybody notices.
The technique behind reaching it safely is the more interesting part.
For me, that is what separates freediving from simply diving underwater and seeing how long I can stay there.
A good dive is not the one where I pushed myself the hardest.
It is the one where I stayed controlled from the surface, through the descent, at depth, through the ascent and all the way back to a full recovery.
Then I can breathe up, reset and decide whether I want to go again. I usually do. 👍🏼
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