A modification of radar tracking of float-drogues used in examination of slow-moving water currents in lakes is described. Up to 10 units are tracked and the direct plotting of float positions on acetate overlays, arranged above a radar display unit, permits an immediacy of visual assessment of water movements. Subsequent corrections for wind drifts yield true flow velocities. The method provides a reproducible and reliable Lagrangian technique for monitoring surface and subsurface current patterns. Examples of its application in a Scottish fresh-water loch are presented.