The Tension Leg Platform (TLP) is vertically moored at each corner of the hull minimizing the heave, pitch and roll of the platform. The resulting small vertical motion allows for less expensive production equipment than would be required on a semi–submersible. Sato et al. developed a basic planning method to design TLPs based on a customer's requirements. It begins with the design of the deck dimensions and layout and the determination of the weight of the on-board equipment. The construction of a TLP at sea presents many engineering challenges. The numerical response of a TLP subject to wind and wave loading was compared to the empirical results obtained by scaled tank testing by Vickery. Springing is a steady state response due to first and second-order wave diffraction sum—frequency effects. A TLP's response due to ringing resembles that of a struck bell. Its amplitude builds quickly and then decays slowly.