Abstract: The invention relates to a boom structure in an oil-spill-combatting system. The principle of the apparatus is as follows: from the water craft (2) there extends to each side a boom, and the ends of the collecting rope (4) are secured to the ends of the booms. The oil is recovered from the rope by running the rope (4) through an apparatus (3) which is situated at the aft of the craft (2). The rope is run first in one direction and then in the opposite direction. According to the invention the rope is put into effective use, up to the last meter, by making the booms from two sections (5, 6), of which the outer one (6) turns synchronically with the passage of the rope (4) and brings each rope end alternately next to the recovery apparatus (3).