I must disagree with your premise. The boat has a tremendous amount to do with the safety of the passengers, and the outcome of any accidents. My BP is now up, so I'm going to rant back.
First off, I ran a charter boat for 17 years. We had a reputation of being safe to the detriment of our reputation as a$$holes. So be it, my stated purpose was to bring every diver home. I was not sucessful, but it wasn't due to a lack of duty of care on my part. In the beginning, nitrox was a profit center, and we charged a pretty penny for it. $10 a fill. We ran an average of 8 cases of DCS per 3 month dive season. We dove the Flower Gardens, which are deep and remote, offering 5 dives a day. In 2008 I made nitrox inclusive in the trip fee. My DCS rate dropped to zero that day. As I said, we were a$$holes, we insisted everyone dive nitrox, to the point where if you weren't nitrox certified, we gave you a certification class. If you wanted the card, you had to buy that. Poof, My incidence of DCS dropped to zero. For the following 8 years, I never had anyone get bent.
But the real issue is not what happens in the water, the boat crew can't do MUCH about that, except describe what is unacceptable behavior and carry through with whatever penalties are described for that behavior. For instance, it was considered to be unacceptable in the Spree to run out of gas. If you ran out, you sat out. No exceptions. It was considered unacceptable to surface in deco. You did, you sat until your computer cleared. 24 or 48 hours. No exceptions, unless you were wearing 2 computers. It was considered unacceptable to surface without your buddy, unless you had a good story, or if you were a solo diver.
But back to after you surface. A responsible boat crew makes sure you are back on the boat. A responsible captain makes sure they made sure. A responsible boat makes sure that all first aid equipment is there, ready to use, and in working condition. We had a fatality in Key West yesterday. No AED on the boat, and the O2 kit had a regulator and hose, but no working mask. A dive boat had no working O2 kit. A dive boat had no working O2 kit. Did that sink in yet?
I saved a life last week on another boat. Pretty happy to have one in the win column. Wasn't a diver, but it took all of my skills, an AED, an ambu-bag, O2, Oropharyngeal airway, and plenty of help. I ran a liveaboard with 7 crew so I could have plenty of help and still get underway.
So, yes. The dive boat absolutely has a responsibility to make things not go pear shaped. And regarding profits. I owned the Spree for 14 years. I made a profit in 4 of those years, 1 when I sold the boat, and 3 when I had winter jobs other than diving. Running a dive boat where safety is job 1 and customer service is job 2 is hard on the bottom line. What it does is create an absolutely loyal client who places safety above all else. That was the client I was looking for, it was the client I cultivated, and I didn't want the other kind. That was hard on the bottom line too. I enjoyed an 80 percent return customer rate.
And in 18 years I was never sued for something I did or didn't do. Or for anything else.
Love, love, love this. Posts like this is how I have been able to learn what to start looking for in a dive shop and or a boat.