People like to quote that 40% DAN statistic as an argument against solo diving, but the reality is that it's really more an indictment against buddy diving as it's commonly practiced. Read it again ... "Forty percent of the fatalities took place during a period of buddy separation" ... those people weren't solo diving, they were diving with a buddy and screwed up.
Buddy separation is not solo diving ... it's diving a broken plan, with all the anxiety, task-loading and lack of preparedness that entails. These accidents didn't happen because these people were alone, they happened because they didn't pay attention to what they were doing. That's how they got separated from their dive buddy in the first place ...
... Bob (Grateful Diver)