Here's a link to the long thread called Scubamau diving accident.
The version I remember is that Opal intended to do a very deep bounce dive, but went a good deal deeper than intended (there was speculation perhaps narcosis was a factor). Gaby went after her to rescue her. She later died; I don't know what kind of shape he ended up in.
But let's be mindful Opal owned the dive operation, and Gaby was on staff. The people involved should've known what they were getting into, and chose to take the risks.
My point is, when we talk about the safety of a dive op., I think it's often from the perspective of the potential customer...would this dive op. be unsafe to dive with? I don't recall any complaints of unsafe dive practices with the regular customers.