LEGO Submarine

Can you build a working submarine from LEGO blocks? Well, I certainly couldn't, but the guy behind Brick Experiment Channel did it. Most of it is LEGO parts, some are homemade, and some are just convenient, like the syringe. This submarine is controlled by Raspberry Pi and PID. This gadget even has laser sensors, a camera, and remote control. It also has a cute minifig captain inside.  

If you want to skip ahead to see the submarine work, that starts at about three minute in, but I was quite impressed to see the quick build. If you want to build your own, the complete project is laid out in a series of articles here. (via kottke)