Floating Production Storage and Offloading (FPSO) platforms are positioned in open sea using turret mooring systems and so Do Floating Liquefied Natural Gas (FLNG) platforms. The behavior of water inside the turret pit influences the platform operations considerably and hence a proper design and study of this aspect become essential for an efficient system. In the present work, the water column oscillation inside the turret of an FLNG during a tow condition at different speeds is studied. The natural periods of water column oscillations inside the turret moonpool are determined by performing decay tests in CFD environment. Free surface elevations at different locations inside the turret moonpool are analyzed both in time and frequency domains and the major natural modes are identified when the vessel is towed at constant speeds. It is found that the piston motion decays faster and sloshing motion remains for longer duration. © 2015: The Royal Institution of Naval Architects.