Cross strut (1) suitable for maintaining a distance between two facing panels (2) of a box caisson (3), the cross strut comprising a central body (5) which is suitable for being inserted inside a wall (6) realised for packing the box caisson (3) itself and two longitudinal peripheral sections (7) which are arranged on either side of the central body (5) and which are each suitable for extending outside the relative panel (2); whereby the cross strut comprises barraging means (11) which are arranged around and integral to the central body (5) between the peripheral sections (7) in order to block the movement of any kind of liquid along a longer longitudinal axis (A) of the cross strut (1). <IMAGE>
