Trends in scientific diving: an analysis of scientific diving operation records, 1970-2004.

A detailed trend analysis was made of 8611 scientific diving operation records undertaken at the Dunstaffnage Marine Laboratory between 1970 and 2004. The analysis represented 15 711 separate person dives and a total of 285 512 minutes of diving time. Specific trends were highly influenced by predominant project areas during specific periods of the analysis. However, most diving was relatively shallow with only 0-12% of annual dive duration at depths of 30m or greater, and the majority (32-87%) being in the 10-29m depth range. Diving was undertaken throughout the year and average dive depth and duration were not influenced by month. One incident of decompression illness (DCl) occurred within the dives analysed yielding a DCl incidence rate of 0.12 per 1000 dives or 0.06 per 1000 person dives. This level of incident is within the range for previous studies on SCUBA diving (0.07-0.14) but below reported incident rates for wreck and/or multi-day recreational diving (0.25-0.49). However, it is suggested that true inter-sector comparisons of estimated risk to the individual diver can only be made when expressing DCl rates in relation to person dives. Average numbers of divers per dive in 'at work' operations will usually be below two; some recreational dives may have many more than two divers per dive.