YouTubers TheSlowMoGuys showed up to their picnic with a watermelon but without a knife! Good thing they had roughly 500 rubber bands and a good idea up their sleeves.
Based on a Japanese YouTube video that they saw, Gav and Dan wanted to try to cut their watermelon open with a bunch of centralized pressure from rubber bands. Not to give the ending away, but they enjoyed the result so much that they did it again and again -- and then, of course, in slow-mo.
They were also prompted to bring up the inevitable question, "Do you reckon if you did that to a human head it would eventually cave in?"
Here's the above-mentioned Japanese video for reference: