One of the things that you need to know about Diving is the science behind it. There are Laws of Physics related to Diving, and understanding them are imperative to your safety while exploring the depths. Since we dive into the depths of the ocean and other water bodies, we must understand how pressure and temperature changes greatly affect our body.

We rely mostly on our Scuba Diving Gear in order to breathe and stay underwater longer. Moreover, keeping the right Buoyancy is affected by your weight, gear carried, and manner of breathing. These, among other things, are very important to know and understand for your own safety and enjoyment.

Physics Principles Used in Diving

Below are a list of some of the most important principles you should be familiar with if you are interested in or participate in the sport of scuba diving.


Beginner’s Guide – Physics Principles in Diving In layman’s terms, Buoyancy is the ability to float. In Physics, it is an upward force on something that is immersed in a liquid or gas. Buoyancy enables an object to float or make it look like it is lighter. Archimedes’ principle states that “any object that is wholly or partially immersed in a liquid is buoyed up by a force equal to the weight of the liquid displaced by that object.”

In other words, the object will float if it is less dense than the liquid where it is displaced. This is called positive Buoyancy. On the other hand, the object will sink if its density is greater than that of the liquid. In this case, it is termed as negative Buoyancy. There is also neutral Buoyancy, wherein the object and the liquid have similar density.

Take note that saltwater has salts which make it denser than freshwater. Hence, if we apply the principle that ‘the liquid is more buoyant if it has greater density’, saltwater is more buoyant than freshwater.

In Diving, if you have positive Buoyancy, staying clear off the reefs is an easy task. Using Diving Weights can increase your total weight, making your density greater than the water, therefore, you will sink. It is important to have the right Buoyancy which is often referred to as neutral buoyancy, but learning how to find and keep the right Buoyancy takes practice and a lot of time.

Gas Laws

Knowing the different Gas Laws can help you understand the behavior of gases underwater. There are several Gas Laws in Physics which have something to do with Scuba Diving. These are: Boyle’s Law, Charles’ Law, Dalton’s Law, and Henry’s Law.

Boyle’s Law

According to this law, there is an inverse relationship between pressure and volume. If the pressure increases, there is a decrease in the volume of gases. This is the case as long as the temperature remains constant.

Pressure changes as you go deeper. If there as an inverse relationship between pressure and volume, there is a direct relationship between the pressure and density of a gas. If you are wondering why Divers consume their air supply faster as they go deeper, this is because of the fact that as the pressure increases, the volume of the gas decreases and it becomes denser. Moreover, the volume of the gas is denser at twice the atmospheric pressure than when it is at the surface.

Charles’ Law

This states that unless there is a change in the pressure of a fixed mass of gas, there is a direct relationship between temperature and volume, that is, as the temperature increases, the volume also increases.

In Diving, pressure increases as you go deeper. You must remember that when you breathe, the pressure must be similar to that of the water. To make this possible, a Diving Regulator is used in which the Divers breathe through. This is a system of valves that reduces the pressure of the compressed air contained in the Diving Cylinder, making the pressure the same as that of the water.

Dalton’s Law

According to the Dalton’s Law of partial pressure, ‘the total pressure exerted by a gaseous mixture is equal to the sum of the pressures that would be exerted by the gases if they alone were present and occupied the total volume’. This implies that each of the gases does not react to each other.

In general, breathing gases are a mixture which is composed of oxygen and one or more inert gases. A safe breathing gas should contain enough oxygen. It should not have carbon monoxide, carbon dioxide, and other harmful gases. Moreover, the breathing gas should not reach toxic level when it is used at high pressure.

As the Diver goes deeper, there is an increase in the pressure inside the lungs and the pressure of the water at the same level as his lungs. To maintain a constant volume, the Diver uses the regulator to take in more gas.

Water pressure increases as the Diver descends, and there is also an increase in the number of gas molecules in a given volume. This results to more intakes of individual gases when the Diver breathes at depth. Take note that even safe gases such as oxygen and nitrogen can be toxic when under pressure. When the partial pressure of nitrogen increases, more nitrogen is dissolved in the blood. When the blood has a higher concentration of nitrogen, it may impair nerve impulses and result to effects similar to that of alcohol. This will lead to a health risk called Nitrogen Narcosis.

Henry’s Law

When we relate this to Diving, Henry’s Law states that ‘as pressure increases, the quantity of gas absorbed by the tissues of the body increases’.

As the Diver goes deeper, the pressure of the surrounding water increases. On the other hand, it decreases as the Diver ascends. When this is the case, higher concentrations of inert gases are absorbed by the tissues of the body.

If the Diver ascends fast, the surrounding pressure decreases, making the absorbed nitrogen to be released quickly, forming micro bubbles in the blood. This will result to Decompression Sickness. To avoid this, it is important to ascend correctly. If the ascent is slow enough, the tissues will be able to slowly release nitrogen. A slow ascent, together with Decompression Stop, reduces the volume as well as the number of formed bubbles so the Diver will not get any injury.

These are some of the principles that you need to know when it comes to diving laws. Learning and understanding the different Physics Principles related to Diving is one way of helping you get started with Diving.