OK, not much interest in expensive high tech defense items. I have noticed on many of these discussions that one possible option to a boat boarding at anchor/mooring is to simply run away from the miscreants by jumping over the side when menaced.
It would seem like this idea has some merit as most boat people are typically good swimmers, and where I am in the tropics, the water
is warm enough to not complicate the issue with hypothermia. Something I have noticed about my catamaran
and it likely applies to most boats is that it is really difficult to see an object that is next to the hull
because of the curvature, so if the miscreant wants to maintain a visual on you they will have to lean out over the side. It seems like this would provide an opportunity to bring them into the water
with you if you felt that this would improve your tactical situation - especially if you used a handy gaff to reach up and accomplish this (most of us likely have a sturdy and sharp gaff on the boat which could be reached from the water). Such an action may well take the miscreant by surprise causing them to drop any weapon - in any event, the sudden fall from the deck
into the water is likely to cause momentary disorientation - especially if this is happening at night. One might note that since you are likely out of reach in the water from someone on the deck
with a machete, this does pose the risk of bringing the miscreant closer.
Being in the water also provides other options - especially on a catamaran
where a shallow dive puts you under the bridge deck where you mostly can't be seen at all. Another option is to move to the small wooden boat in which the miscreant(s) likely arrived - assuming that they wanted to make a silent approach and plan to depart with some of your stuff they need to carry. In my area these are small narrow double ended plywood
boats with outriggers and only a couple inches of freeboard - relatively easy to swamp by depressing one end. Swamping their getaway boat means that they will likely have to abandon their boat and swim away - with a lot less of your stuff. If they abandon the boat, there are two further possibilities - first, it was stolen and the owner will appreciate its return; or, it was their boat and you now have a link to the miscreant as everyone will know who's boat it is.
If you had triggered lights and alarms before jumping in the water, it is likely that they will be looking around for a way to flee your boat; and when they do, you can return on board and notify the authorities - if any can be reached. Has anyone else considered such a contingency plan?