{"id":227,"title":"Shark Attack Test- Human Blood vs. Fish Blood","description":"Mark Rober, a former NASA engineer, designs a human-shaped shark cage to test a long-standing myth about sharks' reaction to blood. After a previous experiment showed sharks were indifferent to human blood, he hypothesizes they will react strongly to fish blood. Teaming up with Shaq and Dude Perfect for Shark Week, his plans are delayed when he tests positive for COVID-19, but he eventually makes it to the Bahamas via a private jet. The new experiment confirms that sharks are far more attracted to fish blood than mammal blood, leading to the main event: Rober entering his custom cage in the middle of a shark feeding frenzy he created, resulting in a terrifyingly close and chaotic encounter.","slug":"shark-attack-test-human-blood-vs-fish-blood","creator":"MarkRober","duration":996.414694,"tags":["Mark Rober","sharks","science experiment","engineering","Shark Week","Discovery","Bahamas","underwater","scuba diving","Shaq","Dude Perfect","animal behavior"],"transcription":"This is a specialized human-shaped shark cage I designed. And this is me in the middle of a shark feeding frenzy in that cage, which as it happens, doesn't actually keep the sharks out. They're in the freakin' cage! But to understand how I ended up in the middle of the Bahamas with buckets of blood surrounded by a butt ton of sharks, we've got to go back exactly one year. Because that's when I ran a test to see what really happens if sharks smell a drop of human blood in the water. For that experiment, I pumped out 15 drops of human blood per minute for an hour pretty close to a bunch of sharks that in the end just weren't really that interested. So this busted the myth from the movies that sharks are these ruthless killers that just go crazy if they smell a drop of your blood from a mile away. But those results made me really curious if the sharks would react differently to fish blood versus human blood. And if they did go crazy for fish blood, could I use that to put myself right at the center of a shark feeding frenzy? And so to satiate my curiosity, my friends at Discovery helped me make my way back to the Bahamas as part of Shark Week this year. But this time, I wouldn't be alone. What up, Robes? Oh, wow, Mark's jumping in on this. What's up, y'all? Look, last Shark Week, a shark tried to kill me. I figured we'll have a little bit of science with Rober, a little bit of fun with Dude Perfect, and a little bit of me. All right, y'all ready to do this? We were born ready, sir. All right. Chop, chop, let's get to it, fellas. We will not let you down. Looking forward to it. See you. Yeah, I've got this idea for a build to just really get me in close with the sharks. Uh, last year, I was in the water. Rober, Rober. That was me saying I'm finished with the call, bro. No. Of course. Yeah. All right, see you guys later. Let's get to it. Let's do this. Looking forward to it. See ya. And so under the direction of Shaq Diesel, it was time to head to the Bahamas. All that was left was to swab my nose to prove to the Bahamian government that I didn't have coronavirus. The only problem was my test came back positive. And this just made me really sad because not only was I going to miss out on this epic adventure, but as far as I was concerned, I was basically just waiting to die. And I had to interact with my family through the glass door to the backyard using a laser pointer, and not even Fat Gus would get within six feet of me. Now, I'm happy to say I eventually beat the Rona and tested negative, but the only problem now is I missed my chance because they were no longer accepting any commercial flights from America. 'Cause we're number one, baby. So I was once again incredibly sad. Until I found a loophole. Because while you couldn't go to the Bahamas on a public commercial flight, there were no rules against going to the Bahamas on a private jet. And since this was the first and last time I would ever have my own personal G6, I acted like I've been here before, like the true professional I am. I mean, mostly. Put Elon on hold and transfer to Oprah. I should mention flying across country on your own plane isn't the most ecologically responsible choice. So while I was in the air, I utilized this website called teamtrees.org, you might have heard of it, to plant enough trees to suck up the carbon not only from my flight, but the next 100 flights this plane would take. In the end, it's important you guys know I'm still super grounded and I didn't let the experience change me one bit. And so now that I was in the Bahamas, the first thing I did was check in with my marine biologist, shark diving expert buddy Luke Tipple, because we need to figure out how to somehow get blood out of a fish. Oh! Just like that. This is how we do it. The first thought is like, can you just freaking blend a fish? Give it a shot. I'll be over here. Dude, you've clearly never seen Will It Blend. There's a whole YouTube channel dedicated to this. Ready? Oh! Okay. I think if we add a little bit of water. Yeah. Oh yeah. Oh yeah, there we go. Oh! This looks like the number 32 from Jamba Juice. We tried a variety of other techniques and eventually started hitting our stride and the buckets started filling up. If I couldn't smell this, that looks pretty delicious. So we've taken about 20 fish with a little bit of help from the blender, turn them into this. If I'm a shark, I'm like, that's freaking delicious. Now that we had five gallons of mouth-watering fish blood smoothie, it was time to get some answers. We already know that sharks don't necessarily go nuts in the presence of a little bit of human blood, but would they go nuts in the presence of a little bit of fish blood? And as a firm believer in the scientific method, it was time to test our hypothesis by heading out to sea. Once we were far enough from land, Luke and I came up with the game plan for the experiment. Basically, we would have two surfboards in the water. One would have a five gallon bucket of our fish blood smoothie, and then another would have five gallons of human blood. We would also have a third board that just had seawater as a control to make sure the sharks weren't just interested in the surfboards. Then we would pump out the contents of each of the buckets over the course of an hour and observe how many sharks approached each board. And then once we know which one they prefer after this, we'll use that tomorrow in the cage just to create the most wild feeding frenzy. Which sounds super fun to me. 'Cause you're not in the cage. And so with the plan in place, all that was left to do was put the boards together and get them out with the sharks. One of the limitations to last year's test was that the boards might have been too close to the boat. So it's possible some of the sharks actually smelled the blood, but didn't investigate it because they were just waiting for a handout from the boat. So this time, we basically placed the boards in the middle of the freaking ocean, super far away from the boat so it wouldn't be a confounding variable. Oh, and I should also mention we ended up using cow's blood because it's really hard to legally find five gallons of human blood. And after talking with a couple shark scientists, they've shown experimentally that all mammal blood essentially smells the same to sharks. So it wouldn't affect the results to use cow blood in place of human blood. So now that all three boards were in place, we double checked to ensure each was anchored down to the ocean floor. Then I just had to start all three custom-built pumps using our custom-built remote trigger, which is the exact moment I realized it must have got busted while being shipped out here because it wasn't sending a signal, which sucks because there's absolutely no way to run the pumps manually. Luckily, a trick I learned while working at NASA is you always build redundancy into your systems, just in case. So we have it in the code that if no remote start signal is received after an hour, each of the pumps will just automatically start up on their own. It's just a feature we never had time to test. So we just had to firmly cross our fingers and hope for the best. I'm hopeful. We've had to overcome a lot to get here for this video. What's one more little challenge? And at exactly one hour, right on cue, the backup code kicked in and saved our whole experiment. With blood now officially in the water, we put the drone in the air and started our observations. And things were pretty quiet for about the first 20 minutes, but then we had our first hit on the mammal blood board. Shark. Shark bait. Oh yeah. Oh yeah, yeah. Oh! But pretty soon thereafter, things started heating up for the fish blood smoothie board. Oh my gosh. There's 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 sharks around the fish smoothie board. And then 10 minutes later, things were only more intense. Here you can see the difference in activity between the three boards. And while you're running an experiment and still collecting data, you really need to keep an open mind. But given what we were seeing, it was getting pretty difficult to remain objective. And so after an hour, we called the experiment and went inside to officially tally up the results using the drone footage. And it turns out the mammal blood board was approached eight times, the seawater control board was at zero, and the fish blood board had a whopping 134 approaches from a shark. It definitely seems like the fish smoothie's where it's at, right? It was pretty obvious. Massive blob of sharks, no sharks. I think that's the go for tomorrow for maximum feeding frenzy. Now that we had a game plan for my feeding frenzy cage the next day, we headed back to shore and to our hotel to get some rest for what was to come. Oh, and fun side note, if the only way to get to a vacation destination is by private jet, it really cuts down on the crowds. We literally had this whole resort to ourselves. Well, almost to ourselves. There were like 40 cats who apparently must also fly private. We woke up bright and early the next morning feeling refreshed and headed right back out to sea where Luke and I prepared some massive bags of fish blood smoothie for me to burst open once I went down. It just seemed like a cool idea to make a cage to get in the middle of a feeding frenzy until this moment. Now that they're making me put on freaking chain mail, makes me reconsider my life choices. If something terrible happens, Shaq, you got to take care of my family because this is all your fault. Yeah, let's go. After several months of prep, unfortunately, it was time for me to get in. It also just so happens I might have forgot to mention this part to my wife. I'm not looking under the water yet on purpose. She might have been under the impression I was just doing another experiment with surfboards and pumps. Sorry, sweetie. Not only was I wearing 10 pounds of steel chainmail for protection, but my vest is also filled with 20 pounds of lead weights. That means I sank pretty fast, but also that the buoyancy to weight ratios were perfect for giving me practice for walking on the moon. Because like many of you, I will definitely go to space in my lifetime. Again, just haven't mentioned that to the wife yet. Now that I had the fish smoothie bags and everyone was back at a safe distance, I just had to pop these stupid things. We knew all along that the most dangerous part would be when I exited the cage, because they'd still be agitated and they'd be stoked to finally have access to the soft chewy center. So the plan was for one of the other divers to distract them way off to the side with the bait box, and then I would get out as silently as possible so they wouldn't notice me. Dude, that was insane. Yeah, you're not so tough now, are you sharks? Okay, Mark. Go ahead, open the door. Okay. Oh crap. That was loud. Dude. Luke. Holy crap. I got to close this back up. Oh, geez. Luke, I need help, man. Holy crap. Geez. Keep your arms in, mate. These sharks aren't going away. I'm going to get you back to the surface. Top side, top side. We are on our way out. I think someone should tell Shaq he can do his own stunts from now on. I'm alive! My main takeaway for me for this experience is that sharks have been on this planet longer than the dinosaurs or even trees have. So they've had 400 million years of evolution to develop these instincts that are rewarded for smelling fish blood. Humans and cows would be an extremely rare delicacy, so it makes sense that it's not just hardwired into their brains. And so with all my limbs intact and with my curiosity satiated, I will leave you with these profound words that in my defense, might have been the Dramamine speaking. As humans, we're always the predator and not really ever the prey. But this gave me a sense of what it's like to be a tuna fish.","timeline":[],"created_at":"2026-04-11 17:33:38","processed_at":"2026-04-11 17:37:40","view_count":1,"thumbnail":"/data/videos/5a714e34-7c19-44b5-a4e1-ce349f7985a6/thumbnail.jpg","video":"/data/videos/5a714e34-7c19-44b5-a4e1-ce349f7985a6/web.mp4","urls":{"page":"/v/shark-attack-test-human-blood-vs-fish-blood","api":"/api/v1/videos/shark-attack-test-human-blood-vs-fish-blood","timeline_file":"/data/videos/5a714e34-7c19-44b5-a4e1-ce349f7985a6/timeline.json"}}