Abstract: A flexible, universal coupling structure for underwater oil lines including an anchored base 1 having upstanding bracket plates 2 defining a horizontal axis 4 between them. A pivot piece 5 in the shape of an open tetrahedron is journalled about the axis 4, and at its upper end has lugs 6 defining a horizontal axis 7 above and perpendicular to the axis 4. A riser column 8-12 is pivoted about the axis 7. Oil or fluid carrying tubes 13 on the base branch into passages 15-18 which converge above axis 7 into tubes 9 and 10. Each passage includes flexible ducts 20, 22 joined by an intermediate curved and inclined tube 21, with the ducts 20 being aligned on axis 4 and and the ducts 21 being aligned on axis 7.