Man Drops Blood Into Sea To Test If Sharks Can Smell It From 1 Mile Away And Was Shocked By What He Found

Ever since I first watched Finding Nemo and witnessed the scene where Bruce the great white shark loses his composure from just a whiff of Dory's blood, many movie-goers have come to accept this depiction as the ultimate truth.

They fully believe in the animated portrayal of Bruce's reaction.

Pixar

There's a widespread belief that these intimidating creatures can detect blood in the water at incredibly low concentrations.

Lots of people are convinced they can sense it from as far as one mile away.

Mark Rober, a former NASA engineer who's now making waves on YouTube, had believed this too.

He's been eager to test this theory "for as long as he can remember" - and in July 2019, he finally did.

The 44-year-old chose a location 20 miles offshore in the Bahamas, known for its shark activity, to carry out his experiment.

YouTube / @MarkRober

He was accompanied by marine biologist and shark diving expert, Luke Tipple.

Mark shared with his audience that he had devised a "robust test procedure" and even constructed some "NASA-grade hardware" to challenge the long-held belief that sharks drop everything at the scent of blood.

He said: "I planned to test just how far they could smell a single drop of blood in the water, but first, I wanted proof that they actually preferred blood over any other scent."

To conduct his experiment, he set up four surfboards in the ocean. 

Each board was equipped to pump out two liters of different liquids: fish oil, cow's blood, seawater, and urine.

Over the span of an hour, these fluids were released into the water. 

Mark and Luke monitored the situation from their boat, using a drone to capture footage of how many sharks approached each board.

YouTube / @MarkRober

Mark showcased his intricate setup, which allowed him to control the pumps simultaneously with a radio signal from the boat. 

He explained: "Each surfboard has a waterproof receiver box that also holds the battery, a custom printed circuit board and two Arduinos."

He then demonstrated: "Then I have the remote control and as soon as I hit this button, they all start pumping at the same time."

For the first ten minutes, there wasn’t much activity near any of the boards, which Mark noted was quite reassuring for those who fear bleeding or urinating in the ocean might draw sharks.

He remarked: "So far it's pretty interesting, we've shown that if you have a massive cut and your bleeding out, and there's this many sharks within like 50 yards of you, they're kind of like, 'Meh'.

"Already an interesting finding, right? You'd think a little bit of blood and there'd just be a massive swarm, but that's not the case so far."

The activity began to increase after 20 minutes, though the sharks did not swarm to any particular board.

YouTube / @MarkRober

At the experiment’s conclusion, they observed that four sharks were drawn to the fish oil, none to the seawater or urine, but the board with the blood attracted a staggering 41 sharks.

Mark added: "Now that we've debunked some surfing myths about urine and proved that sharks definitely have a strong preference for blood over anything we tested, the real question is, just how much blood is interesting to them?"

For the next part of his study, Rober brought on a local phlebotomist to draw blood from himself and some crew members, rather than using cow blood again.

They attached four full bags of blood to two boards, replicating the initial setup, with seawater in the middle as a control group.

"The board on the left would pump the human blood slowly at one drop a minute, the right would pump the blood fast, on average one drop every four seconds," Mark detailed.

He noted that even though the rapid pump seemed excessive, it was "40 times less" than the blood used in the first part of the experiment.

Discussing his results, the former Apple product designer stated: "Over the course of an hour, zero sharks checked out the control board, zero sharks checked out the slow blood pumping board and exactly zero sharks checked out the fast one.

"This was by no means a perfect experiment, but I think it's safe to qualitatively say that if no sharks came to check out 15 drops of human blood a minute, in the middle of shark-infested waters, you're probably going to be OK with a small scrape.

"I mean, there certainly won't be some kind of feeding frenzy with a single drop of blood from all sharks within a mile."

Turns out, Finding Nemo might have stretched the truth just a bit.