Watchly Safety Review

Testing if Sharks Can Smell a Drop of Blood

Mark Rober

13:23 · 124.4M views · July 28, 2019

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Minor FlagsReviewed June 2026

4Minor Flags

1No Issues

This shark science video is safe and genuinely educational for most kids, combining real marine biology with hands-on experimental design in an exciting ocean setting. The host models scientific thinking, curiosity, and respect for wildlife, though some brief crude humor around urine collection and the presence of blood (animal and human) may not suit the youngest viewers. Overall it's a high-quality, engaging piece of science content that demystifies shark behavior rather than sensationalizing it.

Content Breakdown · 5 Categories

Strong & Crude LanguageA little

No profanity or strong language appears in this video; the closest instance is mild exclamations like 'Oh my gosh' and 'Holy crap' used in moments of excitement.

See evidence (2)

“'Holy crap!' - exclaimed during shark encounter”

“'Oh my gosh' - used during feeding frenzy moment”

Realistic Violence, Threats & WeaponsA little

No realistic violence or threats are present; a hand spear is briefly mentioned as a camera mount for an underwater photography experiment, not as a weapon, and no threatening behavior occurs.

See evidence (1)

“'I secured a 360 camera to the front of a hand spear' - used purely as a camera rig, not a weapon”

Hidden Advertising & Sponsored ContentA little

The video is transparently produced in partnership with Discovery Channel for Shark Week, which is clearly disclosed in the description and mentioned in the transcript; Bose is tagged but not promoted within the transcript itself.

See evidence (2)

“'I had with my friends at the Discovery Channel six months ago' - partnership openly stated”

“Description: 'thanks to Discovery for putting my life in danger' - humorous but clear disclosure”

Low-Quality, Extreme & Stunt ContentA little

While the video involves swimming with sharks in open water which carries inherent risk, it is framed as a structured scientific experiment with professional supervision rather than a shock-value stunt; the risk is contextually justified by the experimental design.

See evidence (2)

“Swimming with sharks without a cage after reviewing experimental data”

“'I was willing to try diving with the sharks without a cage'”

Playful & Fantasy ViolenceNot present

One brief jest — 'Oh gosh, I'm gonna die. Save me Luke' — is clearly playful hyperbole during an exciting shark encounter and does not constitute meaningful playful violence content.

See evidence (1)

“'Oh gosh, I'm gonna die. Save me Luke. They can sense I'm a newb.' - clearly comedic exclamation during shark dive”

What Parents Need to Know

This video follows a science YouTuber who travels to the Bahamas to rigorously test whether sharks can detect blood in the water — a genuinely well-designed experiment with real marine biology guidance. Kids will learn about the scientific method, experimental controls, Arduino-based hardware, and shark sensory biology. There are a few moments of crude humor involving urine collection (played for laughs but not graphic), and the video shows bags of cow's and human blood used as experimental materials, which is presented matter-of-factly rather than gratuitously. The host dives cage-free with large tiger and lemon sharks, which is exciting but could be mildly frightening for sensitive younger children. The overall message is strongly positive: sharks are misunderstood animals, fear based on ignorance is reduced through knowledge, and the video actively debunks the myth that a drop of blood triggers a feeding frenzy. There is a brief mention of a Discovery Channel partnership, but it does not function as a product advertisement.

Talk to Your Kids About

1What made this experiment better than the MythBusters test, and why does the way you design an experiment matter so much?
2The video showed that sharks were attracted to blood but not to urine or plain seawater — what does that tell us about how sharks find food in the ocean?
3The host said he felt less fear of sharks after learning more about them. Can you think of another animal that people are scared of that might actually be misunderstood?
4If you were designing your own shark experiment, what question would you want to answer and how would you test it?

Testing if Sharks Can Smell a Drop of Blood

Protected Viewing

What's This Video About?

Scientific proof Pixar sits on a throne of lies. Also, thanks to Discovery for putting my life in danger. Links for the build instructions: https://www.dropbox.com/s/iqn14ydzqafhws5/SharkBait_Manual_PartsList.pdf?dl=0 Sean's Hodgin's channel who did most of the heavy lifting for making the boxes: https://www.youtube.com/channel/UCE-bw6PRKuDlH6fP1mP4nOw Pump animation made by the talented Jared Owens: http://youtube.com/JaredOwen Connor was the beast feeding the sharks underwater. He has some amazing footage for licensing and his own YouTube channel. YT: https://www.youtube.com/channel/UC5fn3MXGv41LY-BB8XRjyCQ email: sharkmanconnor@gmail.com Insta: @sharkmanconnor Follow my marine biologist friend Luke Tipple on Instagram- https://www.instagram.com/luketipple/ More info that was promised- What is likely happening is that the sharks can smell the blood but it's just not in a quantity that is interesting to them especially since they don't love human blood that much (btw, I spoke with a marine biologist and mammal blood is all the same from a chemical marker stand point so cow blood is a suitable substitute for human blood). If I did the experiment again, I would want to test human blood vs. fish blood. This is the most definitive study done to date in a control lab environment on what is least and most interesting to them: The Biology of Sharks and Rays Peter A. Klimley and Steven Oerding; ISBN-13: 9780226442495. Particularly pages 134-140. Figure 6.7; Table 6.2 Thanks to these folks for providing some of the music in the video: Ponder - https://youtube.com/@Pondermusic Laura Shigihara - @supershigi Andrew Applepie - https://soundcloud.com/andrewapplepie Blue Wednesday - https://soundcloud.com/bluewednesday MERCH- They are soft- https://teespring.com/stores/markrober Summary: I've always wanted to test if sharks can really smell a single drop of blood in the water from 1 mile away. So I went to the Bahamas in shark infested waters and set up an experiment to get to the bottom of things. MERCH- They are soft- https://teespring.com/stores/markrober PLEASE CONSIDER SUBSCRIBING: http://tinyurl.com/MarkRober-Sub **************************************** I make videos like this once a month all year long while supplies last: CHECK OUT MY CHANNEL: http://tinyurl.com/MarkRober-YouTube FACEBOOK: https://www.facebook.com/MarkRoberYouTube TWITTER: https://twitter.com/#!/MarkRober INSTAGRAM: https://www.instagram.com/markrober/

Frequently Asked Questions

What age is this video appropriate for?

We recommend this video for children aged 10 and up. The scientific content is engaging but involves bags of animal and human blood, crude humor about urine, and cage-free diving with large sharks, which may unsettle younger or more sensitive children.

Is there anything scary in this video?

The host dives cage-free with tiger and lemon sharks, and there are a few tense moments where sharks swim very close to him. However, the tone remains lighthearted and no one is harmed, so it is unlikely to be genuinely frightening for most kids over 10.

Does the video show real blood?

Yes, the experiment uses bags of cow's blood and later human blood drawn by a phlebotomist, shown on screen as part of the scientific setup. It is presented clinically and matter-of-factly, not in a gory or disturbing way.

Is this video educational?

Very much so. It demonstrates the scientific method including experimental controls, variable isolation, and data review, and it teaches real facts about shark sensory biology. A marine biologist co-leads the experiments, adding credibility.

Is the video sponsored or does it promote anything?

The host mentions a partnership with Discovery Channel's Shark Week as the motivation for the trip, but there is no product promotion or call to purchase anything. It functions more as a collaboration credit than an advertisement.

Does the video encourage kids to do anything dangerous?

No. The host repeatedly emphasizes safety, works alongside a certified shark diving expert, and the overall message is that understanding animals reduces unnecessary risk — not that kids should attempt anything similar on their own.