Ocean currents are one of important resources of ocean energy. Although it is not widely harnessed at present, ocean current power has a vital potential for future electricity generation. In fact, several turbine systems have been proposed in the world. In the present, we consider what factors should be considered in designing the system from the perspective of hydrodynamics. As an example, a floating Kuroshio turbine system which is under development in Taiwan is employed to serve as the case study. The system consists of five major parts; i.e. a foil float which can be employed to adjust the system submergence depth, a twin contrarotating turbine system for taking off the current energy, two nacelles housing power generators, a cross beam to connect two nacelle-and-turbine systems, and two vertical support to connect the foil float and the rest of the system.