A review is presented of estimates for the grid resolution requirements for wall-resolved and wall-modeled large-eddy simulation, of flows with an important influence of turbulent boundary layers. The estimates are described within a classification scheme which is formulated based on the grid resolution relative to the length scales of the turbulent boundary layer. The grid resolution estimates are then applied to discuss the computational cost of ship hull hydrodynamics simulations, both in model and in full scale. The hulls of one submarine and one bulk carrier are included in this discussion. Two simulation cases are included in the paper to demonstrate a complete simulation methodology, to illustrate the implications of the grid resolution estimates, and to investigate the resulting predictive accuracy. The first simulation case consists of fully developed turbulent channel flow, for which a comparison is made with direct numerical simulation results. The second simulation case consists of the flow around an axisymmetric body, which is based on a bare-hull version of a generic submarine model, and for which wind tunnel measurement data are available for validation.