The dynamics of mooring lines for deep water applications with submerged buoys attached to them are studied both experimentally and numerically. First, the theoretical background is outlined. The experimental set-up, as well as the data acquisition procedures, are then detailed. This is followed by a presentation of the obtained results and their comparison with numerical predictions using both time and frequency domain computer codes. Very good correlation is obtained. Finally, the beneficial effects of buoys in reducing the mooring line dynamic tension is shown, provided that proper selection of their size, number and location is performed.