First thing, dial 911.
Report clearly what you have seen, where !
Then get the name/ID of the person you report
to, not just a "staff title" if your are able.
Getting their name/ID gives them incentive to promptly
report "your report" !
With all respect, I am not sure you have thought the matter through. Cell phone service does not extend to the open ocean. And bullying/intimidation often achieves the opposite of the desired behaviour.
The goal is to ensure that the message is credible, that it gets to someone with actual authority, and that action has been taken.