The world’s oceans and continental margins remain a research frontier because of their importance to petroleum exploration and their link to catastrophic submarine mass movements (geohazards). Sediment failures near the shelf edge are the common cause of gravity-driven downslope processes, such as slides, slumps, debris flows, and turbidity currents. Slumps and slides move downslope as a coherent mass. A slide moves on a planar glide plane and shows no internal deformation, whereas a slump moves on a concave-up glide plane and undergoes rotational movements causing internal deformation. A downslope increase in mass disaggregation results in the transformation of slumps into debris flows. Sediment in debris flows is transported as incoherent mass. Debris flows are characterized by plastic rheology and laminar state. With increasing fluid content, plastic debris flows tend to become fluidal turbidity currents. Turbidity currents are characterized by Newtonian (fluidal) rheology and turbulent state. In the world’s oceans, all four processes are important. Seismic profiles and bathymetric images of seafloor are useful for recognizing mass transport as a general category; however, distinguishing a specific process (e.g., slide from slump) requires detailed examination of sedimentological features in core and outcrop.