In the scope of this paper, a first exemplary eddy current sensor for seawater conductivity measurement is developed, based on the derived sensor theory of a previous work. By a high frequency excitation, eddy currents are induced in the fluid and counter-fields measured with a sensing coil. The coils resonance point is used for amplification. The developed prototype is analyzed based on a derived transfer function and FEM-Simulations. The theory is validated using a prototype implementation. With conducted experiments on a sensor test bench, the characteristic were confirmed and disturbances identified. It is shown that frequencies exist, where temperature influence is minimal. This work gives a perspective for a novel sensor to allow seawater conductivity measurement.