An Idea for Next Year using WATER!!

[Jon Stratis]

From the video description, they are Hydraulic arms... in other words, the arms move through transferring pressure from one location (likely the controls held in the student's hands) to another (the pistons controlling the arm) using water (or another liquid) as a medium. Similar to pneumatics, except water is much less compressible than air. As a result, you don't have a big reservoir of pressure like we do with pneumatic storage tanks - instead, the pistons move when you squeeze the controls, with roughly equal volume displacements in both locations (in order to be equal, you would need a perfectly non-compressible fluid, but it's close enough)