The paper presents a case history of the sub-surface investigations carried out in 1967/68 as part of the Morecambe Bay feasibility study. The planning, scope and methods of execution of the investigations are described, together with the effect of field limitations on the data obtained. The results are summarized and discussed in terms both of the overall stratigraphy of the Bay sub-surface, and also the properties of the principal strata, namely the two main sand layers and the various clays and silts. Particular reference is made to the in situ and laboratory permeability testing of these strata, to the obtaining of relatively undisturbed samples of the sands, to the fabric of the clays and silts and to its effect on their shear strength. The application of the work to engineering design is described, its limitations assessed, and conclusions drawn on aspects requiring particular attention in any future sub-surface investigation of the Bay.