You know this old party trick with breaking a bottle with your hand by creating cavitation? It strikes me that building a larger scale version of this experiment could be really useful for high pressure experiments.

There are three ways you could do this:

1. Put the part under test at the bottom of a cylinder that's partially full of water, ideally with a cone at the bottom to concentrate the force, and then hit the top of the cylinder with an air hammer or a spring loaded hammer (don't underestimate big springs!) that can build a lot of inertia quickly. Exactly the same process as hitting the bottle.

2. Put the part at the top of a cylinder with a piston at the bottom and use a hydraulic system to pull the piston down. You might need to use a different working fluid because water is likely to vaporize faster than you can pull the piston, defeating your vacuum. Below the piston should be more water, because any air that leaks past the piston rings will otherwise spoil the vacuum.

3. The last idea is to fill the bottom of the cylinder with water, and fill the top of the cylinder with a gas that shrinks in volume when it burns (e.g. Brown's Gas). You light the gas and the collapsing of volume causes the water to rush from the bottom of the cylinder to the top. You could further improve on this design by using a piston to push the water in the bottom of the cylinder up, thus compressing the gas and creating more energy in the collapsing cavity.

- A thought that I can't get out of my mind, is the possibility that Stanley Meyer et,al actually DID create a water engine, but they didn't understand it, because what was actually happening was fusion. Not cold fusion, but normal high pressure high energy fusion, and the energy to trigger it was caused by cavitation from the collapse of Brown's Gas when ignited in the cylinder of the engine...