We have AC but rarely use it. Even last summer in Grenada we simply switched on the fans (3 in our cabin) and opened the hatches. We lock the saloon door and the hatches in the other parts of the boat. We have motion detecting, high intensity lights in the cockpit that are not activated by wave action or lines moving. A person, or the occasional trespassing bird will activate them. No siren, but we keep an air horn close at hand. Our security lights are extremely bright and I think they are enough for reasonable security (during the night) at anchor.