Wave energy extraction requires the conversion of the energy within the waves to drive the power take off system, often by means of a principal interface, or collector. This paper describes part of the development of a robust, systematic method of optimizing the collector shape to improve energy extraction. In this study, the collector geometry uses a parametric description based upon bi-cubic B-spline surfaces, generated from a relatively small number of control points to reduce the dimensionality of the search space. The collector shapes that are optimized have one plane of symmetry and move in one degree of freedom (surge). The cost function used to determine the performance of each candidate solution estimates the annual energy production in two wave climates, based upon data from sites in the north-east Atlantic Ocean and the central North Sea. A control algorithm is used to keep the collector displacement and power delivery within stipulated limits. The overall optimization strategy entails performing repeated runs of the algorithm for a fixed number of generations, then selecting the best overall result. The shapes obtained for each wave climate are compared in terms of size and performance and marked differences are observed in each case.