What is the letter group designation after a diver has been to 80' for 20 minutes, surfaced for two hours, and then did a repetitive dive to 60' for 25 minutes?

To determine the letter group designation after the described dives, it’s essential to consider the dive profiles and the effect of surface intervals on residual nitrogen levels.

In this scenario, the diver first descends to 80 feet for 20 minutes. After surfacing for two hours, the diver performs a repetitive dive to 60 feet for 25 minutes. The initial dive would contribute to nitrogen absorption, and the two-hour surface interval allows some of that absorbed nitrogen to off-gas, helping to reduce the diver’s nitrogen saturation.

When calculating the letter group designation, dive tables or dive computers are used to assess both the depth and duration of the dives as well as the time spent at the surface. After the first dive, the diver's initial group would be based on the time and depth. After the two-hour surface interval, the diver may move to a new group, and when they complete the second dive, their nitrogen loading will be evaluated again based on the parameters of that dive.

The correct answer of letter group designation 'B' indicates that after the two dives and surface interval, the diver's nitrogen absorption is within the range of that specific group according to the dive tables or algorithms. Thus, recognizing how nitrogen loading works cumulatively from the