A stream caused by intense cooling of a water surface is examined in a stratified water body with an inclined bottom. An arising buoyancy flow causes development of convective coherent structures in the form of vertical streams of cooled water. The influence of inclined topography generates the system of active convective eddies, which form closed circulation cells. In case of pollutant emission, these cells serve as stagnant zones, where the pollutant is detained. The evolution of buoyant oil fractions emitted into a water body due to leakage from an underwater oil pipeline is studied.