The general aim of the Project ''Cohesive Sediment'' of the MAST programme ''G6 Coastal Morphodynamics'' is to advance the knowledge and modelling of physical processes related to cohesive sediment in coastal environments. Bette insights are given into deposition modelling, consolidation theories and associated constitutive relationships, laboratory experiments of liquefaction by waves only or combined waves and currents, modelling of flow-sediment interaction and turbulence in the water column, and the conduct of laboratory erosion experiments. Short term recordings of deposition events, wave effects, consolidation and bottom turbulence in muddy environments emphasise the distance which remains to be covered in order to understand and predict the processes in the field.