You should document your dives and training in a logbook. This serves as a record of your diving experience which you can reference in the future when you need to recall information about a specific dive or your total experience.

Typical information documented in a logbook includes the dive's location, depth, duration, date, time, water conditions, and notes about the general experience or what was seen during the dive. Information about your total dive history including number of dives and total time in the water is also included in the logbook.

Dive operators and instructors may require that you provide a logbook as verification of your experience before accepting you for dive activities or training.