Surface Interval — What It Is and Why It Matters
A surface interval (SI) is the time spent out of the water between dives. During this period, your body continues to off-gas residual nitrogen absorbed during the previous dive. Longer surface intervals allow more nitrogen to be eliminated, restoring more of your available no-decompression limit for the next dive.
Your dive computer tracks surface interval time and uses it to calculate your residual nitrogen loading for repetitive dive planning. Minimum recommended surface intervals vary by depth and duration of previous dives, but most training agencies suggest at least one hour between recreational dives, with longer intervals for deeper dives.
Frequently Asked Questions
How long should my surface interval be?
A minimum of one hour is commonly recommended for recreational diving. Longer intervals are advisable after deep dives, multiple repetitive dives, or if you plan to fly afterward. Your dive computer calculates the optimal interval based on your actual tissue loading.
Does my dive computer track surface intervals automatically?
Yes. Once you surface, your dive computer switches to surface interval mode and continuously calculates how much nitrogen you are off-gassing. It uses this data to compute adjusted NDLs for your next dive.
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