Most easily accomplished at the end of Indrik's level in chapter 4; there's two sharks that spawn on the far side of the pit in the very final part of the stage, where there are a bunch of barrels strewn about. Wait for one to pick up and throw a barrel, then slow down time, grab a barrel yourself, and chuck it at the barrel. This requires some amount of timing; it is very easy to miss. If you use up all the barrels, just reload the checkpoint and try again.