I would like to create a life size lego Bionicle Aqua axe(gali nuva Type or gali master of water Type). The problem is unlike The trident in this video: https://m.youtube.com/watch?v=NK6MWt7vpVE&t=641s
I would like it to be able to be used underwater and not rely on co2. I was wondering if there’s a way to charge a piece of brass/pvc pipe To 500+ psi without co2 gas but still have it compact and waterproof. Another bonus would be if it could not have to be charged with a bicycle pump but rather some system built into the staff.