So I’m here today in Florida filming with Kevin more commonly known as TheBackyardScientist. That’s right! And today we’re going to take these two live grenades, and we’re going to be dipping them in this tub of liquid nitrogen. So go ahead and hand them to me. And then- DUDE! BABY ALLIGATOR! 😀 oh no. So now we’re both about 15 feet away (4.5m) except I’m on land with a grenade on land, and Kevin is in the water, with a grenade in the water. So the question is, which one of us has a better chance of survival? Take a moment to decide, do you dive on the pool deck, or jump in the pool? We both had very different theories for survival. So as firm believers in the scientific method. We decided to test out our hypotheses. So we devised some experiments but before I get to those, I think it’s important to understand how a grenade actually works. So once you pull the pin, as long as you keep this handle pushed down You’re perfectly safe, but as soon as you let go of the grenade. This handle springs off. Which releases a spring loaded striker that hits a percussion cap that starts a 5 second fuse, that you can’t do anything to stop. (Oh great.) but I never really thought about it until I made this video but the reason you see a “waffle” pattern in grenades, is to create weak points in the shell. So that’s where it’s going to break first. And since there are 40 bumps, this grenade is basically an explosion that shoots 40 bullets in all directions. In warfare, that’s what makes them lethal. So the best strategy is to get as far as possible in a few seconds, and then hit the deck with your feet facing towards the grenade. This present the smallest possible target for a flying grenade chunk to hit. So 15 feet away (4.5m) mathematically that puts my chances of getting hit, at less than 1%. (YAY!) But things are even better for Kevin in the pool! It’s been documented that bullets do not travel far in water. At all. The drag force is so high, they just disintegrate after a few feet. So he has a 0% chance of getting injured by a grenade fragment, in the water. But we are thorougher men of science, and we wanted more information. So we designed an experiment, where we filled 3 balloons, half with water, and half with air, to roughly mimic the human body, which is mostly water. But we have pockets of air in our lungs, intestines, in our sinuses, in our ears. And then we subject them to identical explosions, identical distances apart in both air *BOOM!* and water. *Even more BOOM!* As you can see, there isn’t much effect on land because air is compressible. which helps dissipate energy, plus the blast wave reflects around objects. But in water, the story is different. (Woah.) Water is in-compressible. Which means not only is the blast wave not dissipated, but is passes right through your mostly water body. So the air in the balloons, represents the air in your body. Like your lungs, and your sinuses. So basically, what’s happening is the blast wave is pushing in on you, but the air cavities can’t push back with the same force, since they’re filled with compressible air. That means they move a lot, really quickly, which causes permanent damage. As a control, you can see this balloon that is filled with just water. It is perfectly fine. That would be like your arms and legs, which have no air in them, and they are basically in-compressible like water and would be fine. An explosion under water, is sort of like these silver ball things (Newton’s cradle…) So this represents the initial energy of the blast, which then comes down, and passes through the in-compressible water, and then comes out without loosing any energy at the water surface. but now you squish-able lungs are surrounded by in-compressible water, in the path of the blast wave. And so, when the blast happens, there’s a lot of relative motion. Which is bad, if you like your lungs, the way the are right now. (I don’t.) And sadly, our experiment is verified in real life. So the jerks, throw an M80 into the water, and you can see the devastating effect it has on land, if a bird were that close to an M80, it would be startled, but it would be perfectly fine. So now that you know, think back which did you choose? While it’s true, there is a small chance you would get unlucky with the grenade chunk, if you choose to dive next to me. If you choose to join Kevin, you will be in the pool, for the rest of your life. (Rekt.) (Rekt.) So huge thanks, to the TheBackyardScientist for dying, in the name of science! If you’ve never seen his stuff, you just have to check it out. Here’s a video, we just finished filming. It’s a bunch of Oobleck, which is a non-Newtonian fluid, and we destroyed it in every way imaginable. It’s incredible footage, his channel is full of this type of junk, so check it out. Subscribe. And as always… Thanks for watching. So I live, here, and I took a plane to Kevin’s pool, way over here. And on the plane ride, I was listening to the Harry Potter book series. And I know this is quite possibly the least cool and sophisticated audio book recommendation that I’ve ever given on my channel. But I read the books, 15 years ago, and it was really fun to rediscover like a bunch of the little details, that I’d forgotten Plus the dude who reads them, does all of the voices. And he does a really good job. So if you want something fun to do, while commuting, or work around the house. You can rediscover the Harry Potter book series, like me, or you can get any other book for free. All you do is use the link in the description, or go to By supporting Audible you support me, and future plane rides to places like Kevin’s pool. English subtitles by Iowyyn and corrected and made a little more funny by Icy Cubey. Now, go subscribe to Mark Rober.