This paper reports on a continuing study of the mass physical properties of surficial, shallow‐water marine sediments off San Diego, California. Sound velocity measurementsin situat 100 kc were made by pulsing between small transducers inserted into the bottom by diver. Density, porosity, and size analyses were determined on relatively undisturbed samples taken by diver. The following averaged representative values have been obtained:Velocity insediment at ImpedanceDensity Porosity Med. diam 60°F (105g/Sediment type (g/cc) (%) (mm) (ft/sec) cm2sec)Fine sand 1.93 46.2 0.19 5520 3.25Very fine sand 1.92 47.7 0.12 5435 3.18Silty very fine sand 1.68 61.3 0.05 5075 2.60Medium silt 1.69 60.9 0.03 4825 2.49Clayey fine silt 1.60 65.6 0.02 4800 2.34Laboratory measurements of velocity and attenuation 25 to 35 kc were made by a resonant‐chamber method using diver‐taken samples; average attenuation values of about 0.5 db/ft (silt) to about 5 db/ft (fine sand) were obtained. At three stations the sediment sound velocity was less than the velocity in the bottom water.