He's a large, large man.
And that 288-pound man jumped nearly five feet straight up in the air and landed on some boxes. It was 59.5 inches, to be exact. It's pretty clear why nobody could block Watt as he became the NFL's defensive player of the year last season.
The box jump isn't an event at the combine, but here's some numbers to put Watt's jump into context. In May, Seahawks receiver Justin Veltung became a bit of an Internet sensation for a 56-inch box jump. People were very impressed by that, and it is a great feat. Now keep in mind that Veltung is listed at 183 pounds, which is 105 pounds less than Watt. And Watt beat Veltung's jump, which everyone freaked out about, by three-and-a-half inches.
Here's another comparison: At the combine, one of the typical tests is the vertical jump. The top mark at this year's combine was a 43-inch jump by Seahawks 221-pound running back Christine Michael. The two jumps aren't the same of course (a person lifting their legs doesn't count in the vertical jump), but Watt's leap was still more than 16 inches more than Michael's combine-best performance and again, Watt is a defensive lineman.
Just watch the YouTube video. Again and again. Tell us when you actually believe you saw a 288-pound man pull off that athletic feat. We'll be over here shaking our head.