After completing a dive to 24 metres and waiting 39 minutes, what is the pressure group after a second dive to 18 metres for 25 minutes?

To determine the pressure group after a second dive, it's essential to understand how no-decompression limits (NDLs) and pressure groups are established using dive tables or dive computers.

After completing the first dive to 24 meters, the diver will have accumulated nitrogen and will have a corresponding pressure group based on exposure time and depth. Waiting for 39 minutes allows some nitrogen to be eliminated from the body, which may affect the pressure group before starting the second dive.

During the second dive, going to 18 meters for 25 minutes means the diver will be adding more nitrogen to their system. The dive tables indicate the maximum allowable time at various depths, and by referring to the specific dive tables or a dive computer, we can calculate the new pressure group.

Considering the second dive's parameters, the accumulated nitrogen from the first dive and the time spent at the second depth, you arrive at the pressure group of 'T'. This indicates that the diver is within safe limits without exceeding no-decompression limits for the second dive after the necessary waiting period.

Understanding pressure groups helps divers manage their nitrogen loading and makes safe diving practices. This scenario illustrates the importance of timing and depth in calculating the impact of each dive on a diver’s overall nitrogen levels.