Well, since everyone else got to toss in his/her two cents' worth:
1. Echoing several posts, there is NO excuse for leaving a diver(s) behind.
2. Personally, I appreciate someone naming names in this type of "offense", which is one of -- if not the -- most serious failings that I can imagine for a dive boat. And...See item 1.
3. There are a boatload of divers -- IMHO, most casual divers, who are what most of us are -- who would have a very, very difficult time swimming a mile on the surface in the ocean. Being able to see the shore is a lot different than being able to get there. Accordingly, leaving a diver behind is inherently dangerous and life-threatening, no matter where it occurs. And... see item 1.
4. Generally, the only people who are hot to file a lawsuit are people who haven't been in one. And it doesn't make much difference whether you're plaintiff or defendant. The best case still breeds a mess that even the most ardent plaintiff often wishes he/she had never started. It's even worse if one is in a lawsuit in a state (or even a city) where one doesn't live. In short, a lawsuit is a action of last resort, and any decent lawyer will say exactly that.
5. Even if someone won a lawsuit in these circumstances, it's likely to be the operation's insurance carrier that pays the claim.