If your vessel goes down, you can don a life jacket and, one hopes, crawl into a life raft. Few vessels, however, are equipped with fire-retardant suits or breathing apparatuses. A smoke detector, therefore, becomes the first and possibly most important line of defense in dealing with the dangers of flame as well as the toxic smoke it’s almost certain to cause when modern boatbuilding materials burn. The device is also likely to be the least-expensive piece of equipment you’ll need to guard against fire. Once a fire takes hold, fire extinguishers, both portable and fixed, become the next option, one that you’ll want to avoid exercising at all costs. Virtually every fire extinguisher, even the smallest economy models, cost more than most smoke detectors, and if you need them, it means you’ll almost certainly sustain at least some costly damage. You get the point: Smoke detectors are cheap insurance.