This paper describes an improvement in techniques currently used for mesh deformations in fluid–structure calculations in which large body motions are encountered. The proposed approach moving submesh approach (MSA) is based on the assumption of a pseudo-material deformation applied on a triangular coarse mesh to significantly reduce the CPU time. The computation mesh is then updated using an interpolation technique similar to the finite element method. This method may be applied on structured as well as on unstructured meshes. An extension to complex boundaries undergoing large rigid-body motions is proposed combining the MSA and an encapsulation box. The influence of the coarse mesh on the quality mesh is discussed.