Scuba diving is a relatively fascinating activity as long as you are well aware of pressure physics. Not knowing how physics works can be extremely dangerous since it could lead to sickness or even death in some cases.
Scuba Divers deal with pressure by going through decompression stages as they are descending to their desired depth. Without taking these decompression stops, the diver may suffer from the bends.
The danger of decompressing doesn’t come from when the diver is deep underwater; it is dangerous if they ascend to the surface too quickly. So here is more information on how water physics works and why divers need to take these decompression stops.
Understanding the fundamentals of underwater pressure
When you dive deep down into the water, your body needs to deal with the effects of pressure. At sea level, the air pressure surrounding us is calculated as 1 atmosphere (atm) or 1 bar. For every 10m down, the air pressure doubles. This is because water density is 800 greater than air; therefore, it exerts a greater force on your body.
As you keep descending for an additional 10m, the body pressure increases by 1 bar. Reflect on the table below to understand the psychology of pressure underwater.
According to Boyle’s Law: Air volume = 1 / air pressure
| Water depth | Bar/atm pressure | Air volume in our bodies | Density |
| Sea level | 1 | 1 | X 1 |
| 10 meters | 2 | ½ | X 2 |
| 20 meters | 3 | 1/3 | X 3 |
| 30 meters | 4 | ¼ | X 4 |
| 40 meters | 5 | 1/5 | X 5 |
Analyzing the two theories – Boyles and Henry Law
Two schools of thought analyze the effects of pressure on a diver.
According to Boyle’s Law, there is an inverse relationship between pressure and volume for a fixed gas mass at a constant temperature.
- As the diver descends, the water pressure surrounding him increases, causing a reduction in the volume of the air in his body.
- Similarly, as the diver ascends, the water pressure around him decreases, causing air to take a larger volume (expand) in his body and scuba gear.
This means that as the air volume in our bodies declines, we become less buoyant. At this point, a diver is suggested to equalize four air spaces- ears, sinuses, mask, and lungs.
Safety rules
- Always breathe in and out without trying to save air by breath-holding.
- Ascend and descend slowly to avoid severe injuries.
According to Henry Law, at a constant temperature, dissolved gas in a liquid is directly proportional to gas pressure. As pressure decreases, gas becomes less soluble and comes out of the liquid.
- When a diver descends deeply, high pressure is exerted, which will make our bodies absorb more gases. When nitrogen enters the human body with compressed air-breathing, it causes bends.
- The pressure rate decreases when the diver ascends, and the tiny bubbles enlarge. As you reach the surface, the bubbles become the size of the balloon. It can lead to decompression sickness and blood blockage to critical organs.
