A few years I visited a shop that had a waterjet machine. Water is pumped to about 60,000 psi, it exits a nozzle at the cutter head in a stream of .010 diameter and a speed of mach 3 ( speed of sound X 3) a tube surrounds the nozzle and Garnet very fine. flows into the tube and is picked up by the water. This abrasive is what does the cutting, carried by the high speed water. It uses big 60hp plus motors, and very very clean water. The pumps are built with ceramic pistons and cylinders Big $$ I'd guess. High Maintenance for sure.