The AquaSquirt The AquaSquirt works on the principle of the Newton's Third Law of Motion. "For every action there is an equal and opposite reaction" This is the same way rocket engines work. They throw out gaseous "matter" in very large, very high speed volumes, thus propelling the rocket in the opposite direction. Instead of hot gases, the Aquasquirt ejects a large, high speed volume of water out of two thrusters located beneath the boat under the water. Each "thruster" has a piston which changes geometry automatically when it retracts, so as not to suck water back into the thruster cylinder. Thus maximizing thrust on the push, but minimizing suction on the retraction. With this configuration, the thruster need not be a completely sealed system. See working diagram below: Face of Opened Plunger with Gasket Back of Opened Plunger showing Hinges Back of Plunger in Closed Configuration The following photos were taken in our state of the art marine testing facility Feel the THRUST! Would make a helluva water gun! NOTES: So far, it's working really good! Relatively easy to push in the piston quickly by arm, yet very easy to retract due to the hinges on the piston working properly. I'm not anticipating any problems with the linkages required to make it pedal powered. Next step, put it on the boat with the linkages and maybe hook up the flex tube at the end for the steering. The boat is intended to have steerable thrusters for vectored thrust!