Today in the submersibles department our hacker [Rupin Chheda] wrote in to tell us about their submarine project.This sub is made from a few lengths of PVC piping of various diameters. There is an inflation system comprised of a solenoid and a pump, and a deflation system, also comprised of a solenoid and a pump. The inflation and deflation systems are used to flood or evacuate the ballast which controls depth. There are three pumps for propulsion and steering, one central pump for propulsion and two side pumps for directional control, allowing for steering through differential thrust. Power and control is external and provided via CAT6 cable.We have covered various submarine projects here at Hackaday before and it is interesting to compare and contrast the designs. One sub we covered recently was this one made mostly from Lego. There are considerable differences in the approach to buoyancy, propulsion, steering, power, and control. Whereas the PVCSub uses separate ballast inflation and deflation systems the Lego sub uses one system that can be run forward or backward; whereas the PVCSub uses a pump for propulsion the Lego sub uses a magnetically coupled propeller; whereas the PVCSub uses differential thrust for steering the Lego sub uses a small propeller; whereas the PVCSub transmits power through external wires, the Lego sub has an onboard battery; and whereas the PVCSub uses the power wires for control the Lego sub is radio controlled.Just goes to show that there are many ways to skin this particular kind of cat.