We have developed a 3-term liquid/solid, strong contrast reflection equation and have used it, with an empirical V/sub P/ reflectivity relation, to invert the sea-floor seismic reflection to determine V/sub P/, V/sub S/, and density. Applying this technique to pre-stack data from a Caspian Sea 3D multichannel survey, we find that a submarine flow from the Absheron mud volcano, offshore Azerbaijan, has much higher seismic velocity and density than surrounding sea floor. We propose that this flow is enriched in high-density clasts of country rock - xenoliths - raised from depths of as much as /spl sim/9 km by the mud volcano. In contrast, onshore subaerial flows are predominantly low-density frothy gray clay. The 3D seismic data and gravity data further suggest that high-density, high-velocity regions near the mud volcano and buried up to 1000 m below the sea floor are stacked Pleistocene sea-floor mud-volcanic flows. These bodies appear to buttress slumping fault blocks.