articulated relative to the base the whole having a positive floatability so that the upper edge of the flap is even with the surface of the water application_number US 201314077605 A description in fig1 the device according to this invention has been shown adapted to work with a skimmer of a pool this device comprises a base 10 with a width greater than that of the skimmer 12 on which it must be placed the skimmer 12 has a window 14 that is the opening itself and a peripheral frame 16 that is held against the wall of the pool particularly to ensure the seal when a liner is present this frame 16 penetrates into the opening while creating an interior peripheral projection 18 the height of this base 10 is approximately that of the skimmer 12 with which it must work the base 10 has a front face av and a rear face ar the rear face is the one that is intended to be pressed against the skimmer and the front face looks out at the pool this base 10 has a flap 20 articulated relative to the base and above said base around a hinge 22 this flap 20 is articulated to pivot relative to the base preferably toward a face of said base in this case toward the rear face ar of said base as will be.