I find this hard to credit, and frankly it makes your instructor (for one) appear to be a rumor monger. A first-person account posted in the comments section of a news source recounts:
Hard to deny first-person accounts, but from what I saw a few beaches away (i couldnt see the incident, only the boats responding to the incident), it looked like the monterey express took off once the rescuers began their search, and before the kids were found.
Dont take that as a hard fact but does anyone know if the express stayed on scene during the search once the CG and FD showed up? As hard as it might have been to 'abandon' the teens underwater, I can see how they wouldnt want to get in the way of the search operation, and not have the other divers view their friends being brought up from the bottom.