A modular and integrated optimisation model for the design of underwater vehicles is presented. In the proposed optimisation model two modules (i.e. low fidelity and high fidelity) are incorporated and the basic geometric definition of computer aided design (CAD) is integrated with computational fluid dynamic (CFD) analysis. The hydrodynamic drag is considered as single objective with constraints on the geometric parameters of dimension, space and volume. The CAD model is implemented in MATLAB∗™ and CFD model is implemented in Shipflow∗∗™. A real-world design example of an existing underwater vehicle is presented. The applicability of proposed optimisation model is shown. The presented results show that within given set or sets of constraints the application of optimisation model in design results into an efficient hull form. © 2016, DESIDOC.