Dive log guides

What your dive computer records, what the numbers in your logbook mean, and how to use them on your next dive.

• Air consumption (SAC rate): how to work it out and use it
  How to calculate your surface air consumption (SAC) in litres or cubic feet a minute, with worked examples, and how to plan gas with it.
• No-decompression limit (NDL): what it is and why it changes
  What your NDL means, what shortens it, a table of limits by depth for air and nitrox 32, and why your dive computer and your logbook disagree.
• Tissue loading: what the percentage means and how it falls
  What tissue loading means on your dive computer and in your logbook, how it relates to your NDL, and how fast it falls after a dive.
• How to read a dive profile
  What the depth graph of a dive shows: descent, bottom time, ascent rate and the safety stop, the shapes worth knowing, and what they say about your diving.