The characteristics of a convective single plume developing from a hydrothermal lake source of radius R have been investigated. The study was motivated by the aim of estimating velocity and buoyancy scaling laws obtained from numerical models of convection from isolated sources of finite extent. This has been done for the case R/H < 0.7, where H is the water column depth, and for the case of baroclinically stable convection. The single plume described hereafter presents the following characteristics: 0.35 < R/H < 0.64, RD/R > 25.8, where RD is the Rossby radius of deformation. From the results, the density anomaly scales with the buoyancy flux Bo applied over the source and the depth according to g′ = (3.81 ± 0.06) Bo2/3/H1/3, and a single vortex is maintained around the forcing disk with a mean radial velocity scaling according to Ur = (1.57 ± 0.43) Bo1/3R/H2/3. The experimental results described here will be compared to the results found for the numerical model by Okada et al. (2004).