The first dive is to 60 ft for 50 minutes. You spend one hour and 40 minutes on the surface, what is your adjusted maximum dive time at 60 ft?

The first dive is to 60 ft for 50 minutes. You spend one hour and 40 minutes on the surface, what is your adjusted maximum dive time at 60 ft?

• A. 8 minutes
• B. 2 minutes
• C. 4 minutes
• D. 6 minutes

Answer: (C)

The key idea is repetitive diving and residual nitrogen. When you dive, nitrogen saturates your tissues and you carry some of that nitrogen into subsequent dives as residual nitrogen. The amount you can safely bottom-dive at a given depth on a subsequent dive depends on how long you’ve been on the surface (the surface interval) and the depth and duration of the previous dive. A longer surface interval lets more nitrogen off-gas, but some residual nitrogen may still affect the next dive, so the no-decompression limit for the next dive is adjusted accordingly. With a first dive to 60 ft for 50 minutes, there is residual nitrogen to consider. After a surface interval of 1 hour 40 minutes, the repetitive-dive table (or a dive computer) shows a very limited additional bottom time at 60 ft to stay within no-decompression limits. In this case, that adjusted maximum bottom time is four minutes. So the next dive at 60 ft should be limited to about four minutes to remain within the safe no-decompression range given the prior dive and the surface interval.

The key idea is repetitive diving and residual nitrogen. When you dive, nitrogen saturates your tissues and you carry some of that nitrogen into subsequent dives as residual nitrogen. The amount you can safely bottom-dive at a given depth on a subsequent dive depends on how long you’ve been on the surface (the surface interval) and the depth and duration of the previous dive. A longer surface interval lets more nitrogen off-gas, but some residual nitrogen may still affect the next dive, so the no-decompression limit for the next dive is adjusted accordingly.

With a first dive to 60 ft for 50 minutes, there is residual nitrogen to consider. After a surface interval of 1 hour 40 minutes, the repetitive-dive table (or a dive computer) shows a very limited additional bottom time at 60 ft to stay within no-decompression limits. In this case, that adjusted maximum bottom time is four minutes. So the next dive at 60 ft should be limited to about four minutes to remain within the safe no-decompression range given the prior dive and the surface interval.