I can see how the boat would be a large source of attrites, but how does ACM get people? Is it airsickness or does it just require a type of skill to accomplish?
Flight school ACM is simultaneously very canned and very dynamic. There are really only two ways a fight can go from a neutral start, but things happen very quickly, there is a steep learning curve expected, and you can't break training rules.
Most guys I saw get downs in ACM when I went through were for training rules violations; either repeatedly busting the 10,000ft hard deck or the 500ft bubble around each jet. An especially dim view is taken of busting the hard deck and not calling it versus realizing you've screwed up and calling "knock it off" before you actually go below. Of course, if you're already scraping by, any down can hurt.
I'm not sure I ever saw anyone attrited specifically for bad ACM performance; one guy in my class got two downs and a resulting PRB in ACM. They pulled him off my boat det and made him go through with the PRB, but then it clicked. He finished out ACM, went to the next boat, and winged with us. It looked bad for awhile, but he fought through and went to Lemoore.
As for the boat, you get two looks, and I think in my time in Advanced I only heard of one person who double-DQed. Most people figured it out the second time if they DQed once.