Caves are overrated. Food is impossible to get without venturing out, electrical power can only be supplied from outside, water can be challenging (especially wastewater removal), the complete lack of light and prevalence of mold can be bad for your health. Even fresh air supply might be a concern in some cases.

Personally, I'm leaning toward a solar-powered sailboat as the perfect 'ride out the apocalypse' strategy.

• You can easily relocate to distance yourself from all kinds of threats, avoiding wars, disease outbreaks, etc.

• Water can easily be supplied via desalination 'water makers', powered by your solar panels. In the event that this goes wrong somehow, you can also resupply by sailing up into any navigable freshwater river, or build simple evaporation-based solar desalinators.

• Some of your diet can be provided by fishing. For the rest (and occasional repairs and replacement parts), you can barter at ports of call. No matter what's happening in the world, there will still be people somewhere who are interested in moving passengers and cargo from one port to another. And if global trade is broken down, you may be able to bring valuable barter goods by transporting things that can't be found locally.

• Waste disposal and sanitation is easy; just dump it overboard before sailing to a new location. (Preferably, you'd only dump biodegradable stuff, though, and only in the open ocean, where environmental effects of small dumping will be negligible. But if there's no other choice and you really need to dump some plastic waste or something ... well, the environment can take one more for the team.)