Breaking ship waves are one of the most challenging problems in the field of free-surface hydrodynamics. We aim to produce and implement unique, scalable parallel-computing capabilities for simulating turbulent breaking waves and the resultant formation of spray and entrainment of air. SAIC has developed a Cartesian-grid method for simulating breaking waves around ships. Body-force and finite-volume formulations are used to model the hull and an interface capturing method is used to model the free surface. As a result, minimal user input is required to simulate breaking waves, which makes the tool ideal for ship design studies. At MIT, a suite of codes has been developed based on advanced large-eddy simulation of coupled air-water flows. This suite uses time accurate interface capturing and interface tracking methods to model turbulent free-surface flows. The results of the numerical simulations are used to guide the development of turbulence models for the SAIC code and other codes, such as Reynolds averaged Navier-Stokes (RANS), which are currently being used by the Navy. Through large-scale computations on the IBM SP3 and Cray T3E using both Cray SHMEM and MPI and hybrid techniques, the numerical results and their analyses provide us with the framework to develop models of wave breaking and spray formation and air entrainment. Numerical simulations of various ship-like geometries moving with forward speed and spilling breaking waves have been performed. With these promising results, which were achievable only through high-performance computations, the last frontier of computational ship hydrodynamics will be breached in the near future.