Guns for self-defense are all about fear of the unlikely.
Again, untrue.
I carry a spare tire not because I fear the unlikely event that I might get a flat, but because I'd rather have it and not need it than get a flat tire - which is a possibility, although unlikely - and not have the spare. I've been driving for nearly 30 years, and have driven literally dozens of different vehicles in nearly every state in the continental U.S. In all that time and hundreds of thousands of miles of driving, I have had exactly two flat tires. So although it's highly unlikely, I still carry a spare.
I keep a fire extinguisher in my house and on my boat not because I'm afraid of a fire, but because it's simply prudent to have, to be prepared for the unlikely event that a fire occurs.
I have life insurance, not because I'm afraid I'm going to die, but again, because it's prudent preparation for the unlikely event that something happens - my family will at least be provided for.
I carry tools, a first aid kit, and tapered wooden plugs on board not out of fear, but preparation.
It's about being prepared for potential circumstances, not fear.
Yes, cruising in international waters and foreign ports does add complicating dimensions to the calculus, but a gun is a tool. One must make a reasoned analytical determination whether to equip one's self with one, just like with any other tool.
As for me, I would rather have one and not need it than need one and not have it. Just like a fire extinguisher, a spare tire, a tapered wooden plug, a PFD, a flare gun, life insurance, etc. And just like all those things, I hope I never have to use it for real. I would much rather the situation remain that I don't need it.
I don't sail in international waters - maybe I will someday. But I have a concealed carry permit and do generally keep a .45 in my truck. I don't usually have a gun on my boat, but I have from time to time, depending on where I'm going.