How to Calculate Surface Interval

For scuba divers, surface interval time is the amount of time you need to spend on the surface between dives. Your body needs to recover from the pressure changes that go along with deep-sea diving, and time spent at the surface lets your body return to normal before you subject it to the pressures of undersea diving again.

Things You'll Need

  • RDP tables
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Instructions

    • 1

      Decide the depth and length of time for your multiple dives. For example, say you want to dive for 12 minutes at 120 feet and then dive for 18 minutes at 90 feet.

    • 2

      Go down the 120-foot column on RDP Table 1. At 12 minutes, you're in row J. This part of the chart is gray, which means you need to do a three-minute safety stop.

    • 3

      Go to the back of RDP Table 3. Go across the 90-foot row until you find the number 18 in the blue zone (safe). In this instance, you're in column B.

    • 4

      Look at RDP Table 2 and find the intersection of Row J and Column B. The highest number you see is 1:12. This is the least amount of time you need to spend back at the surface before heading down for the second dive.