The range of interactions between fibre and water and the consequential properties of the bound water are modelled and examined. Dietary fibre may interact with water by means of polar and hydrophobic interactions, hydrogen bonding and enclosure. The results of these interactions vary with the flexibility of the fibre surface. When the fibre is insoluble or junction zones are formed,this may result in profound changes in the surrounding water. Such interactions are capable of affecting the structuring and solvation properties of water well away from the immediate surfaces involved. In particular, the specific properties of water enclosed by dietary fibre are examined, an area of investigation previously receiving scant attention. The way this enclosure may affect the properties of water is exemplified by modelling the colon to show how fibre may exert a beneficial action by the preferential partitioning of hydrophobic carcinogens. Unfermented dietary fibre has a tendency to form low-density expanded water that acts as a preferential solvent for hydrophobic molecules when compared with the less-structured denser water within the much more hydrophilic mucus layer.