Abstract: Method of collecting light-weight substance floating on a liquid surface, for example, oil floating on water, said light-weight substance being carried into a collecting reservoir, in that on the outer side of a wall of the collecting reservoir extending below the liquid surface, away from the liquid surface, a down-stream is produced by which the light-weight substance with liquid is passed beneath an edge of the wall located beneath the liquid surface and into the collecting reservoir, after which the light-weight substance rises up in the reservoir to the liquid surface, where it is collected, while the liquid is conducted away through at least one outlet near the bottom side of the collecting reservoir.