Remotely-sensed data are presented from a sequence of overflights of the marine effluent discharge zone of a coastal power station complex. Emphasis is placed on studying the buoyancy-driven spreading of the thermally-enriched cooling water discharge from the power station outfall, under slack tide conditions. The results of the study show that the effects of local topography upon the spreading mode can be dominant under these conditions, and that the presence of solid barriers to the spreading flow can lead to complex deformations of the temperature field. It is demonstrated that simple reflection of the buoyancy-driven surface flow by islands results in the generation of localised regions possessing both high velocity shear and convergence. Surface foam lines are then formed within these regions. Data are presented to show the coincidence of the foam line positions with the edges of the surface plume, and this coincidence is discussed in the context of the flow patterns inferred from the thermographic data.