a. the risks that diving down to 50 metres can entail, b. physical and medical preconditions, c. surface-supplied diving, d. progression diving down to 50 metres, e. complications in connection with diving, f. use of a hyperbaric chamber, g. use of wet bell, h. use of a warm-water wet suit, i. operational conditions, j. diving equipment, k. common types of work equipment, l. common types of breathing gas, and m. diving supervision.