Use a hollow steel ball with a threaded steel  plug.   Immerse in water
   to fill.  Thread plug, close tightly.   Immerse in liquid nitrogen
   behind a strong shield.  Water will shortly freeze, but cannot expand.
   Eventually, the container will explode due to increased pressure.

   On Wed, Dec 1, 2021 at 6:33 AM, Karl
   <gmkarl@gmail.com> wrote:

   I'm not sure how to build a bomb out of water.