Understanding the power balance of a swimmer, who needs to overcome power losses to drag and to water set in motion, requires detailed insight into the hydrodynamics of the flow around the swimmer. This will be done from a hydrodynamic point of view with techniques familiar from fluid mechanics. One of our objectives is to develop a system to visualize the flow around a swimmer in practice. Currently, the visualisation system is designed and built and we will present the underlying ideas of the experimental setup.