How does one actually build a remotely operated under water vehicle, ROV for short? Which components must be developed from scratch, what is available off the shelf? Where can one find required, dormant knowledge? How does a vehicle of this kind orient itself? How does one teach the vehicle a hint of autonomy, i.e. "thinking" or "intelligence", respectively? Which fascinating parallels can one draw to contemporary space exploration? And how does heavy machinery look like after having been submerged under water for decades? We embark upon an expedition into both the known and unknown, through modern information technology, software, electronics and robotics as well as unexpected corners of the "deep sea" of central Germany.