A device (10) for a skimming operation for petrochemical or chemical fluid storage or process tanks working by gravitation, comprising buoyancy means (20), means (30) for collecting surface fluid to be skimmed including an opening (31) emerging just above the interface between the fluid with density d1 and the fluid with density d2, as well as connection means (32), and discharge means (40) for the collected surface fluid. The discharge means (40) includes at least two flexible pipes (41, 42) connected symmetrically to the connection means (32) and extending vertically in the fluid with density d2 toward the bottom of the tank.