Quiet does not mean "introvert".Sure, any idiot -- introvert or not not -- could have caused this problem. And not only the introvert, but the DM and Captain may have shown questionable judgment in handling the situation. I'm not a DM nor a Captain, so I'm not really in a position to judge their actions. But after this experience, I'll forever associate silent introverts with accidents waiting to happen.
I do believe that the DM would have stood a better chance of averting the incident if she had more clearly been able to identify this diver's combination of lack of skill and lack of a buddy, and at least kept a closer eye on him. His reticence didn't help.
Interested to hear a DM's perspective on this incident.
Making mistake does not desert to be labelled as "idiot".
I fail to understand the last part. He was allowed to dive SOLO, wasn't he? So how could you keep a closer eye on a solo diver?