I am not a scuba instructor or even a dive master, however I have been diving for quite a few years and I am concerned about what seems to be a general ignorance regarding dive computers and how to use them (that is; what does the information being displayed on the computer actually mean?).
I regularly go with groups from our local dive club on overseas trips where we do a week or so of repetitive diving. These dives are usually fairly leisurely in respect to depth and profile, but what catches some people out is that there is a steady nitrogen build-up as the trip progresses. This is particularly so with folks who are doing 3 dives during the day then a night dive as well to "get their money's worth" on the trip!
The kicker is that some divers rarely look at their computers during a dive, yes true! So as they blithely continue on the sort of dive that they do on a weekend and they are unaware that their NDL is getting shorter each day. Then on a particular dive, NDL is reached, but they continue on as the same folk tend to rely on others to set the pace and reason as long as they keep in the middle of the group everything is OK and anyway the dive profile is the same as others they have done back home. Add a bit of current and air consumption is increasing as well. They are now unknowingly in deco territory and most likely without enough gas to do a deco stop anyway
Then it's time for the group to ascend and that's when they look at their computer which is now displaying an unfamiliar deco stop display. They have no idea what to do, but follow everyone else. After a safety stop they surface and are dismayed when the computer goes into error mode due to a missed deco stop!
The solution for some is to use another computer for subsequent dives because obviously theirs is faulty! and they don't want to miss any dives on the holiday.
I have witnessed this scenario a number of times, however fortunately, so far, there haven't been any cases of DCI (that I am aware of).
