5 Surprising Items that Would Help You on a Desert Island, According to a Survival Expert

"If you were stranded on a desert island, what would you want to have with you?"

We've all heard the question in some form. Maybe it was asked to reveal deeper character traits at a job interview, or as an icebreaker at a party. Typical answers range from the practical (a canteen of water) to the creative but slightly ridiculous (an endless supply of Buffalo wings). So, what would actually be handy to have at your disposal, should you find yourself marooned on a remote isle? The answers might surprise you.

Survival instructor Tony Nester has been studying survival skills for decades. Before founding Ancient Pathways survival school in Arizona in 1989, Nester spent his childhood hunting and fishing and a four-year period in young adulthood living off the land in caves and teepees across the country. A desert island, Nester says, similar to the wooded wilderness or frigid tundra which his courses for military troops, government agencies, and youth groups have covered over the years, presents a unique set of challenges survival-wise. But as he does for any survival situation, Nester emphasizes the importance of focusing on what he calls The Big Five: shelter, water, fire, signaling, and first aid. And if you heed his advice on these five somewhat unexpected essentials he recommended to Mental Floss, you'll fare better while stranded on a tropical island than your coworker who chose shampoo and their collection of Harry Potter books for entertainment.

1. A MACHETE

Forget the Swiss Army knife—it won't do you much good on a desert island. Because tropical environments are crowded with thick vegetation and tough surfaces, if you wind up deserted in one, you're going to need some serious hacking power. "You're not going to get by well with just a pocket knife, given the nature of what you're going to be harvesting—coconuts, and cutting down palm trees or saplings to make your shelter," Nester tells Mental Floss. The broad-bladed knives are cheap and easy to find if you're already in a coastal region, he says, and the size can depend on your preference, though something in the 14- to 18-inch range would be big enough for heavy chopping and small enough for MacGyvering utensils like bowls or spoons. Good luck bringing it in your carry-on pre-plane-crash, though.

2. A HAMMOCK

We usually associate lounging in a hammock in a tropical environment with a carefree vacation, but Nester says if you're stranded on an island it can be a multipurpose lifesaver. A hammock's most important function in this case would be providing a place for you to sleep that's off the ground. You could use the machete to gather material to construct an elevated platform, but with a hammock you're protected from the spiders, critters, and snakes that are probably slithering around. Plus, you save yourself the time and precious energy all that elevated platform-building would drain. (Side note regarding those slithering snakes: Nester says snake bite kits are no good for your survival arsenal. Research suggests they can do more harm than good.) The hammock could also double as a heavy sheet of fabric when you need it: It could be used as a filtration system (it likely won't purify anything or desalt ocean water, but it could rid stream water of bugs and debris), and could work as a food-catching net, as shade, as a blanket, or as a raincoat.

3. A CELL PHONE (EVEN IF YOU DON'T HAVE SERVICE)

There'd be nowhere to plug it in and you probably wouldn't have service, but a cell phone could still be an important component of your survival. Nester recommends trying to get a text out, putting the phone's strobe feature on at night, or just turning it on for a couple hours each day you're stranded. "You may not be able to get cell reception," Nester says, "and you may not be able to get a message out, but you don't know if your phone's going to be pinging off the nearest tower on the next island, or on the coast, or somewhere else, and that can help searchers on the other end triangulate your location."

4. A SIGNAL MIRROR

No, this isn't what you'd use to start a fire—though having a spark rod to do just that is another top priority item for Nester, right up there with the machete. You'd need to specially order one online, but a signal mirror is a 2-inch by 3-inch glass mirror that is designed to alert nearby planes, boats, or other rescuers that you're there. There's a sighting device in the middle of the mirror that, when held at the right angle toward the sun, sends flashes that can be seen for miles (Nester says he's had flashes seen up to 26 miles away). "It's not taking up any sweat or calories on my end, but that can carry a long way," Nester says. When you're not using the mirror to actively signal, you can hang it from your makeshift shelter or tree so that even if you're sleeping, its glint may be able to draw some attention.

5. A FAMILY PHOTO

Out of all the things that Nester says can help you survive in a dire situation—fishing gear, heavy-duty bug repellant, and storm-proof matches would also make his must-have list—the one item that could really keep you alive is a laminated photo of your loved ones. A fire can keep you warm and a machete can keep you fed, but that picture might just keep you sane. In Cast Away (a movie, Nester says, that still holds up and used his fellow experts in the survival skills community as consultants for accuracy), Tom Hanks's character uses the picture he has of his girlfriend to keep himself going. Wilson the volleyball, though maybe not the first thing you'd think to include on your survival checklist, serves a similar purpose.

"You think, 'OK, this is going to be an ugly night, it's going to be rough,'" Nester says. "'I hurt myself, my ribs are broken, I've got to make fire and do all these things, but you know what? I'm going to be here in the morning when the sun comes up because I'm going to make it back to my kids or my family or my golden retriever.'" The will to survive and your psychological health, the U.S. Air Force Pocket Survival Handbook repeatedly notes, is often a more important factor in survival than physical preparedness. And for Nester, a visual reminder of who it is you need to get back to—"whatever it is that's going to get you through that situation"—is a definite Big Five item.