Publisher Summary The aim of this chapter is to elucidate remotely operated system (ROV) design. The communication and control of underwater vehicles is a complex issue. This chapter begins with addressing the focus these issues: power source for the vehicle, degree of autonomy, and communications linkage to the vehicle. It then moves to the discussion of autonomy, with description of an aircraft analogy and then the vehicle in its water environment. The chapter addresses the most critical areas of ROV design and operational considerations by investigating the premise that vehicle geometry does not affect the motive performance of an ROV nearly as much as the dimensions of the tether. ROV systems are a trade-off of a number of factors, including cost, size, deployment resources, and operational requirement. But the tether design can help create, or destroy, the perfect ROV.