Diving –
Principles of Working at Depth

Key to understanding diving is the concept of pressure, and how it varies with depth. The weight of our atmosphere, approximately 320 km above the earth’s surface, only produces a total pressure of 100 kilopascals. This is known as ‘one atmosphere’ or 1ATA. Since water is considerably denser than air, it creates a high-pressure environment. A depth of only 10 metres is required to produce another atmosphere of pressure. So at ten metres the total or absolute pressure is two atmospheres or 2ATA (200 kilopascals). For every ten metres of seawater, an extra atmosphere is added to the total pressure.