I got the same impression on a cruise ship I traveled on a few years ago. They were very aware of anyone or anything approaching the ship. Besides that, they had a better eye on passengers than most realized. I don't know that all cruise lines are as vigilant.
The vulnerability is when in port, even if on cruise-sponsored tours.
We cruise out of US ports, not going to cruise in Europe. I see where Carnival is suspending stops in Turkey due to stability, etc.