No one is saying the women are powerless. But in this case - as in most cases of such behavior - there was a power dynamic at play. This was exacerbated by the fact that it was part of scuba training, which means underwater, a place where humans are not meant to survive. I’m certain this instructor was fully aware of what he was doing, and I’m certain he has done it many times before. He acted in a predatory manner.When do people have to act as adults? I was subject to long term abuse as an adolescent, so I have some familiarity with it. Children are different than adults and to treat women as weak powerless children will not bring about good outcomes for anyone.
Now, yes, this likely means many women before OP have just let it go and likely managed to rationalize his behavior in some way. And yes, that has allowed him to continue this abhorrent behavior. But HE is the one at fault, not OP for not saying anything at the time.