My son went to college in Pittsburgh, a city with lots of high bridges over deep water. I had a few nightmares, let me tell you. But I showed him some of the cases and explained that I thought the main reason few women fall into bodies of water is that they're much more careful about keeping track of each other. And he and his friends were more careful when they went out, not that they drank much anyway. Maybe that's something you could explain to him?
I did that too. Back with the Shane Montgomery case and then this, Zach Marr, case. I told him about the cases and asked his thoughts on college aged boys going to a bar and then getting separated from the group and heading toward water. I asked him what he'd do if he found himself outside bar and unable to go back in with his group.
Hopefully talking about it is enough. I also talk to my DDs about bad stuff too. I remember I was a kid when the Adam Walsh case happened and my mom had me watch the news coverage with her and she talked openly about the situation...was scary to me but whenever I was walking home from the bus stop, and my parents were away at work, I was well aware of my surroundings. I even walked up to neighbor's door once or twice when I was unsure of a car driving by.