I spent a lot of time on the hook last year, often in remote locations where the only boats I saw were a few commercial fishermen and others just cruising along quietly in skiffs. My worry was that someone would board the boat in the middle of the night to steal something, which is very common in many areas, and I would have to confront them. For this reason, I installed a neat, little infra-red alarm that I purchased from Radio Shack for about $39 many years ago. If the beam is interupted the device sounds a loud wailing electronic siren that can be heard at least 100 yards away. I suspect it would deter any boarder in the middle of the night. The only time it sounded was when a great blue heron decided to enjoy it's supper in my cockpit.
Now, while in Marathon's Boot Key Harbor, there was a series of thefts that took place from the boats of visiting cruisers. A couple locals decided to become industrious and found that generators, dinghies, fishing tackle and outboard motors were easy pickings in the middle of the night. Over a period of two months, they managed to steal more than two dozen generators, a dozen dinghies, 200 fishing rods and reels, several tackle boxes, 30 outboard motors, and more. The perpetrators were eventually caught with the diligence of a dedicated sheriff's deputy who spent many sleepless nights waiting in the dark for the thief to show up.
I believe both of these guys caught were drug addicts, at least from some of the information I was able to garner. Had they been confronted by the cruiser(s), I'm relatively sure they would have had no qualms in injuring or killing the person trying to defend his boat, crew or property. I'm also quite confident the alarm system I have would have scared them off. If not, I would have no qualms employing other tactics to demonstrate their long distance swimming ability.
You gotta be prepared for everything when cruising,