Optional enrichment module. An applied workshop on the NOAA No-Decompression Air Dive Table: the two rounding rules, Chart 1 no-decompression limits and letter groups, Chart 2 surface interval credit, Chart 3 residual nitrogen time and the adjusted limit, and the equivalent-single-dive-time test. Ten repetitive-dive problems are worked from the first descent to the final letter group, followed by the same dive computed on two table systems, what a table cannot know about the diver in front of you, and the errors that produce confident wrong answers.