Water Jet

[Whittman]

Just got a tour of a friends marble/granite company and saw the water jet cutting machine in action. Wish I had something like that underwater!

[ropesfish]

Water jets are pretty cool. Interesting thought about using one underwater. Waterjets typically use pressures of 25,000 PSI to 55,000 PSI and a orifice of .010" to .015" and the water leaves the nozzle at 900-1800 MPH. An abrasive is usually added to the water to provide friction for the cutting. Some do actually work underwater to reduce spray.
Besides the bulky stiff pipes or hoses required to move the pressurized liquid to the nozzle being more than a trifle unwieldy...even with that small orifice it seems to me the reaction force might make it pretty hard to hold on to. )Pictures of divers scooting around backwards like a loose balloon come into my mind's eye.)
This article: http://science.howstuffworks.com/question553.htm that I referenced to make sure my numbers were right has a couple of interesting bits of new information that might make it worthy of reading.

If you try it, post up!

[Whittman]

If I could afford a water jet for underwater use chances are I wouldn't be posting on T-net as the only way I could afford one would be if I found some serious treasure! If you check out techdivetools.com you can see how water jet can be made to balance the thrust. Not sure if it could work with such high pressures though...