Water is one of the most powerful erosion agents on the planet. In most cases we want to prevent this erosion, so it helps a great deal to study exactly how the erosion happens.
http://www.mindbites.com/lesson/8462 for full video
How can the same soothing liquid we drink and bathe in cut through materials used to build skyscrapers?
Adding an abrasive to a high pressure water jet will allow you to cut almost anything.