Robots which exploit their embodiment promise to be more robust, energy-efficient and adaptable. However, the majority of systems designed in this way are only capable of exploiting their embodiment when performing a single task in a single environment. For such robots to be capable of adapting to a range of tasks or environments, they must be capable of adjusting their morphology on-line and have an understanding of how adjustments in both control and morphology affect their behaviour. We introduce the concept of the control-morphology (CM) space and the Variable Stiffness Swimmer (VSS), a multi-segment pendular robot with adaptive joint stiffness. This system allows us to perform an initial investigation into how navigating the CM space affects the behaviour of a robot. We show that the behaviour of the system is not only the result of selecting a particular location within the control-morphology space, but also the route taken to arrive at that point. We also demonstrate locations within the space where a shift in behaviour can be caused entirely by smooth on-line changes in morphology.