Richard Sherman -- That's Not a Cannonball ... DO IT AGAIN!

Here's Richard Sherman on the set of an Oberto beef jerky commercial where he was SUPPOSED to do a cannonball into a pool. There was just one problem .. HE DID A JACKKNIFE!!!

C'mon man.

Everyone knows a cannonball is two hands wrapped around your knees while entering the water ass first ... a la Ron Burgundy.

Watch. Learn. Do it again.