I stayed off of this thread for a long time. I don't know the dive op or Roberta at all, so I really didn't have much to say, except...
I have done a lot of diving in Cozumel, and most have been excellent experiences. I have had a couple that were not so good, but nothing as bad as this, even by Roberta's version of the story.
I once has a DM check the current, and then, incredibly, lead us against it.
I once had the op put together a boat of supposed professionals and mistakenly include a first time diver, leading to a less than stellar dive situation.
I was once mistakenly left off the manifest for my dive, so I had to get on the last slow boat instead of the fast boat I had signed up for.
In the first two, I mentioned the situation to the op--with no expectations that any action would be taken. In the third, I didn't say a word.
In all three cases, my money was fully refunded, without my asking for it.
Since Roberta admitted that the captain made an error that led to a bad situation, perhaps a little more could have been done.