With the advancement of high-performance computation capabilities in recent years, high-fidelity modelling tools such as Computational Fluid Dynamics (CFD) are becoming increasingly popular in the offshore renewable sector. In order to justify the credibility of the numerical simulations, thorough verification and validation is essential. In this work, decay tests for a freely floating cylinder and a linearly moored floating offshore wind turbine (FOWT) model of the OC4 (Offshore Code Comparison Collaboration Continuation) phase II semi-submersible platform are simulated. Two different viscous flow CFD codes are used: OpenFOAM (open-source), and ReFRESCO (community based open-usage). Their results are compared against each other and with water tank experiments. The data from experimental and numerical tests is made freely available on the web hosting platform GitHub 1 , inviting other researchers to join the code comparison and build a reference validation case for floating offshore wind turbines.