Results from a field study of a submarine spring and its associated brackish water plume at the head of Cambridge Fiord, Baffin Island, are presented. Computer-enhanced 1920-kHz acoustic backscatter images yield measures of maximum height of rise, plume geometry, and vertical velocities in the rising plume. Submersible observations indicate that the freshwater discharge is localized, being about 5 m in horizontal extent. A thriving benthic community was found within this area. The initial geometry and water properties of the flow at the vent, together with the ambient stratification and a numerical buoyant plume model, are used to show that the probable freshwater discharge rate lies in the range 0.10 to 0.20 m3/s. Computed vertical velocities on the plume axis are significantly greater than the vertical velocities inferred from scattering structure trajectories in the acoustic images. The decay of acoustic backscatter amplitude as a function of radial distance in the neutrally buoyant spreading plume is comparable to the radial decay of temperature fine structure, and the radial decay scales are consistent with those expected from molecular dissipation of turbulent microstructure. ¿ American Geophysical Union 1990