Abstract: The invention is concerned with a simple and inexpensive device for rapidly removing a first liquid medium floating on a second liquid medium, the first medium having a density less than the second medium and being immiscible therewith. The device of the invention comprises an immersible container means having a bottom opening, a valve for allowing the first and second media to flow into the container through the bottom opening upon immersing the container into the first and second media and for controllably preventing the first medium from draining from the container upon raising the container out of the media, a float member having a density greater than the density of the first medium and less than the density of the second medium, the float member being mobile in the container to move up and down with an interface between the first and second media.