The relationship between pressure and depth is one of the first things that beginners learn in the world of scuba diving. Understanding this principle is key to diving safely and enjoying every dive to the fullest. Are you interested in knowing if the deeper you dive, the higher or lower the pressure? In this article we tell you everything you need to know about this essential principle of diving.
At Dive Academy Santa Pola we accompany you from the first moment to understand how your body works underwater and what happens physically when you descend deeper. Today we explain everything about pressure, air, volume, oxygen and how this affects your dive.
The physics of diving
To dive safely and effectively, it is essential to understand the physical laws that govern the behavior of the body and equipment underwater. Here we explain the basic principles of pressure and gases that directly influence every dive.
Water pressure
With each meter we dive, the force exerted by the water on our body intensifies. This increase becomes an increase in absolute pressure in diving, which is the sum of the atmospheric pressure (1 atm at sea level) plus the water pressure.
As you descend into the sea, the ambient pressure increases by 1 atmosphere for every 10 meters of water column. In other words:
- At 10 meters: 2 atm (1 atm of atmosphere + 1 atm of water)
- At 20 meters: 3 atm
- At 30 meters: 4 atm
This increase has immediate physical effects on the body, the equipment and the way we breathe.
Air pressure
When we dive, we breathe compressed air from a cylinder. This air is affected by the pressure in the scuba tank and also by the depth at which we are diving. As the pressure increases, the gases are compressed and their density increases, which results in a higher air consumption per minute during descent.
This is why it is so important to control the consumption and plan the dive time well, depending on the depth.
At greater depth: higher or lower pressure?
If you still have doubts about whether the deeper you dive, the higher or lower the pressure? The answer is clear: the deeper you dive, the higher the pressure. This rule is based on fluid physics and is a universal constant. Increased pressure affects both the body and the diving equipment, and its implications should be known to all divers:
- According to Boyle’s law, the higher the pressure, the lower the volume (the volume of air decreases). This affects the lungs, the drysuit, the buoyancy control buoy (BCD) and any air-filled space.
- As air is denser, it wears out faster.
- The deeper, the greater the respiratory effort, the harder it is to breathe.
- There is an increased risk of nitrogen narcosis, especially from 30 meters and above.
Table of pressure-volume-depth relationship in diving
| Depth (m) | Absolute pressure (atm) | Relative volume |
| 0 | 1 | 1 |
| 10 | 2 | 1/2 |
| 20 | 3 | 1/3 |
| 30 | 4 | 1/4 |
| 40 | 5 | 1/5 |
Does increasing the depth require a reduction in oxygen?
Not exactly. What happens is that, as the pressure increases, the amount of oxygen we breathe per inspiration also increases. This can lead to a situation of oxygen toxicity if certain thresholds are exceeded.
Therefore, in technical diving, special mixtures such as Nitrox (air enriched with oxygen, but limited in depth) or Trimix (with helium to reduce the effects of nitrogen and oxygen) are used.
In recreational diving, this is usually not a problem as long as the 40 meter limits are respected and standard compressed air is used.
Pressure withstood by the human body
The human body is perfectly designed to withstand diving pressure, up to certain depths, as long as it is done progressively and with proper technique. However, there are physiological factors to take into account:
- Diving and ear pressure: The middle ear is one of the most sensitive points. It is essential to compensate the pressure (manipulation of the Eustachian tube) to avoid barotraumas.
- Air spaces: Sinuses, lungs and teeth must also adapt to the change in pressure. During the ascent, it is essential to maintain constant breathing and never hold air in the lungs.
- Tolerance limit: Although the body can withstand the pressure of recreational diving, the deeper you dive, the greater the risks increase: narcosis, decompression and gas toxicity.
How does pressure affect diving equipment?
Increased pressure not only impacts the diver’s body, but also the diving equipment. Here’s how:
- Regulators: They must be calibrated to operate correctly under pressure, releasing air at the same pressure as the environment.
- Suits: Dry suits can be compressed, so it is important to compensate them properly to avoid a feeling of emptiness or loss of thermal insulation.
- Buoyancy control buoys (BCD): They must be constantly adjusted as the depth changes, since the air inside them is also compressed.
- Masks and glasses: They need compensation to avoid the vacuum effect on the face.
Checking and knowing your equipment well is as important as understanding the physiology of diving.
Tips for safe deep diving
Deep diving opens the door to a fascinating underwater world, but requires special knowledge and precautions. Before you dive, keep in mind, these tips:
- Get proper training with professional instructors.
- Compensates the ears from the first meter of descent.
- Control the air and follow the tables or the dive computer.
- Never dive alone.
- Always perform the safety stop.
At Dive Academy Santa Pola we teach you from scratch and safely. If you want to learn more about the pressure increase in diving, understand how your body acts or live the experience of diving off the island of Tabarca, we are here for you.
Contact us to learn more about our courses and outings, come and discover why we are the reference center for diving in Alicante!
