Liquids can cavitate when subjected to very low pressures. Cavitation in marine applications has consequences ranging from material damage to noise production. Cavitating flows are very challenging to simulate due to the simultaneous presence of both liquid and vapor phases. We are developing the ability to reliably simulate cavitating flows. Examples include LES of sheet to cloud cavitation which is characterized by unstable regions of vapor bubbles that violently collapse as the free-stream pressure increases downstream. Our simulation results show good agreement with experiment.