ABSTRACT The objective of this study is to develop a three‐dimensional numerical model for a floating point absorber wave energy converter in the presence of sea waves, considering its interaction with a bi‐fluid flow (comprising air and water). The primary aim is to create an efficient computational tool that achieves two key objectives: firstly, reducing the computational time typically associated with high‐fidelity Computational Fluid Dynamics (CFD) models, and secondly, curing the lack of accuracy of low‐fidelity asymptotic or projection‐based reduced‐order models in regions subjected to viscous and highly nonlinear effects. To address these objectives, we propose a multi‐fidelity model based on domain decomposition. This approach combines a high‐fidelity CFD solver, which accurately captures the behavior in viscous and nonlinear regions, with a Reduced Order Model (ROM) based on Proper Orthogonal Decomposition (POD), tailored for weakly nonlinear regions. By integrating these components spatially, we simulate the dynamics of the floating body within a unified framework. This methodology ensures precise predictions of the body's motion for both in‐sample (reproduction) and out‐of‐sample (prediction) configurations.