This note is from one of my crewmembers who is a 2nd mate on a container ship.
It is worthwhile reading.
Kimberlite Amel Super Maramu #376
I’m currently in Canada, up the Saguenay River with 590 feet of dynamite on board.. I might be going up to northern Greenland (76 deg North) for a cargo next month.
There is no device on any containers that I have ever seen that sinks containers, they will only sink if water is able to get in, either through a hole in the steel or through the doors.
That’s one of those things you can’t really prevent, if a container is there, you’re not gonna see it unless it’s calm seas.