Western Europe's de-polderisation policy was launched in the 1980's and has since spread along the coasts, especially in the U.K. where it is governed by coastal defence objectives through “managed realignment” and environmental objectives which are predominant elsewhere. Various means of de-polderisation exist: through tidal gates or breaches or sea dike removal. While physical studies on de-polderisation should be continued, it is equally important to examine the social context, favouring or not, marsh restoration since acceptance of any de-polderisation scheme largely depends on public opinion. The results of five opinion surveys carried out in France and the U.K. were thus compared and revealed diverging opinions or unexpected indifference towards de-polderisation. A profile of those opposed shows that they are relatively old and regularly frequent the de-polderised sites or live near them. “Negative” reactions, however, are also linked to a lack of knowledge on the marsh environment and on the impacts of de-polderisation. Other explanations surface as well: the fact that today coastal environments are quite simply viewed as “landscape”, the degree of human intervention in the implemented schemes, the physical and eustatic context and the degree to which people are informed. Public knowledge could be improved and mentalities changed through better communication methods especially on a local level. Furthermore, the creation of a “variables bank” capable of explaining public attitudes and perceptions more systematically would also improve “social management” of the de-polderisation policy.