Just a little story about that. When I started tech diving, we did not use computers at all. We preplanned the dive and followed the plan using bottom timers as our guide. When two divers in our group of friends got bent, they had no idea why--they had followed the plan perfectly. Well, one of them was using a computer in gauge mode, so he was able to get a profile of the dive. It turned out they had not been nearly as perfect as they thought--not even close. Ascent rates, depths, and stop times were far from perfect. These were educated people, one with a Ph.D in afield requiring a high level of mathematical skill.I’ve never used a computer in the water, I plan for a few different scenarios and must stick with one. My dives are solo and 90% are deco so have little wiggle room. I would like to try a computer in the water though.
I think of that whenever I see people say they don't use a computer and just follow a written plan instead. Since they really have no way of knowing, they really don't know how well they followed it.