Abstract: The invention is directed to a method for designing a fluid inlet duct for marine vehicle hull, generally comprises the steps of: (a) determining an inlet duct surface geometry, represented by a series of fifth-order Bezier cross-link curves, within specified hydrodynamic design constraints; (b)generating a panel representation of the surface geometry; (c) calculating the pressure and velocity distributions of the flow within the inlet duct; (d) evaluating the surface geometry; (e) repeating steps (a)-(d) for subsequent iterations of the surface geometry until the specified hydrodynamic design constraints are satisfactorily met at a predetermined design condition; (f) evaluating a resulting surface geometry at off-design conditions; (g) repeating step (a)-(d) for subsequent iterations of the surface geometry until the specified hydrodynamic design constraints are satisfactorily met at off-design conditions; (h) performing a geometric refinement to a fillet region of high curvature in the inlet duct; (i) gener