A former NASA engineer-turned-YouTuber is helping Discovery Channel determine whether sharks prefer human or fish blood in a new “Shark Week” experiment.

Rest assured, there’s no sinister plot to extract blood from their human test subject Mark Rober. Instead, Rober and marine biologist Luke Tipple use cow’s blood as a substitute, assuring viewers that “all mammal blood essentially smells the same to sharks.”

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In the Bahamas, the pair utilized a shark dive-tank in a controlled experiment involving three different types of blood, all released into the water at the same time from a distance from each sample.

The results of the experiment can be seen in the video above.