You can't cut steel in half with water. Waterjet cutting requires an abrasive media like garnet to cut through hard materials. Water is simply the power source that accelerates the garnet to Mach Jesus.
Plain water can cut through aluminum and other thin metals at pressure, and human skin probably isn’t harder than that, but that’s a good clarification for those who are unaware of the additives commonly used for harder materials like steel/thick aluminum/etc. and it was my mistake to say steel originally. Thanks for pointing it out.