In terms of energy, what they experienced was equivalent to being in a pressure vessel the size of an SUV, and having on the floor in the center of the SUV a bomb made of a bit less than 60 pounds of TNT, and that bomb explodes.
That amount of TNT equivalent energy is calculated on the basis of an estimated implosion depth of 8000 feet.
You don’t need any type of shrapnel to enhance the deadly and destructive power of an implosion like that.