The structure of cohesive sediments is controlled by the energy input. At low oscillatory strains, cohesive sediment structure is completely described as an elastic solid. At higher oscillatory strains, the sediment structure is viscoelastic and at very high strain amplitudes the sediment behaves as a viscous fluid. Rheological measurements of cohesive sediments provide a quantitative evaluation of these viscoelastic properties as functions of clay minerology, solution ionic strength, solid concentration and oscillatory frequency. This viscoelastic representation of sediment structure is used to predict the response of such sediments to oscillatory shear. The model predicts bottom sediment fluidization and wave energy damping.