Why Do Grenades Look Like Waffles?
When a grenade with 40 bumps explodes, it's pretty much the equivalent of 40 bullets shooting out in every direction. This is in large part due to the waffle-like texture of a grenade exterior. This waffle pattern creates weak spots in the shell, so that the grenade will break apart in those grooves. If you happen to be near a grenade that's about to blow, get as far away as possible and hit the floor. Lay face down with the bottoms of your feet toward the grenade. And if you can get in a pool or body of water, your chances of avoiding injury are much greater. Due to the drag, bullets don't travel far in water.
from Mark Rober
Key Facts In This Video
As long as you hold the handle of a grenade down, you're safe, even if you've pulled the pin out. (1:08)
It has been well-documents that bullets do not travel far in water at all. (2:01)