I'm sorry for you. You and your sister need to report him to the resort, the agency, and the police. Both of you should make notes while the incident is fresh in your minds and try to recall anything and everyone who was anywhere near the incident or may have seen your reaction/state of mind when you exited the water or while you were in a state of duress. All of these things will help buttress your word, since it is a "he said" /"she said" type of incident. In all likelihood this isn't the first time that this jerk has done this - and he's probably done it in situations that are not dive related also.