My brother was a Mariner...One of his best stories was being on watch and seeing an up periscope come into view right in their path.
It’s all about International waters.
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Its a bit more complicated than that. You can be in international waters and still be in a position to inflict a lot of damage, which is why you may not have the freedom to operate with impunity. Threats of any kind are generally not ignored or warmly welcomed.