We apply a new effective medium model for calculating elastic moduli of high-porosity ocean-bottom sediments to several Ocean Drilling Program (ODP) well log data sets from offshore Amazon delta, Peru margin, and Bengal Bay. The model relates the bulk and shear elastic moduli of the sediment to porosity, differential pressure, elastic constants of the grains, and pore-fluid compressibility. As a result, we can accurately match sonic well log data using porosity and differential pressure as the main inputs. Therefore, velocity data can be used to infer porosity and pressure.