Originally Posted by 2door
Be very very careful trying this. Unless you have a good understanding of metal, welding and the pressures you'd be working with, you could be injured. Hydro forming metal is a job best left to those with the knowledge and the proper equipment. Simply pumping water into a closed vessel without careful engineering could produce a very effective 'pipe bomb'.
You don't know until you try. I hate the mentality of "you have to be a professional blah blah". Sure, you can spend half of your life going to school for something, or you could like, have a little fun in life and just take a shot at it. It would be smart to sit down and do some basic research first, and take a few safety precautions, but at some point in history, there had to be some crazy people to be the first to try something. Plus, water isn't compressible. It wouldn't make a very big explosion anyway. Something needs to detonate very quickly and evenly to make a bomb. Water isn't fast enough and doesn't have enough pressure buildup. It would blow open a hole where all the water would escape from, but it would be very, very unlikely to simply "explode". Any water vessel you have seen explode was from steam / heated water.