Abstract: A connection system between a main body and a superstructure, usable in a sea environment, comprising an arrangement for moving the main body relatively to the superstructure and, guide means cooperating with said moving arrangement. The moving means arrangement is inscribed on a cylindrical surface, was the guide and moving arrangment being adapted to allow at least a swinging movement of main body relatively to said superstructure.

Abstract: The present invention concerns a realization procedure of a modular system particularly suitable for use off coasts, this system comprising a set of cylinders (A.sub.1, A.sub.2, A.sub.3 . . . ) rigidly linked together, this set including at least one central cylinder (A.sub.1) and a plurality of peripheral cylinders (A.sub.2, A.sub.3 . . . ).This procedure includes the following successive stages:the assembling together at the quay (8) of at least two peripheral first cylinders (A.sub.4 and A.sub.5),a joining of the central cylinder (A.sub.1) to these two peripheral cylinders (A.sub.4 and A.sub.5),the placing in water of the unit constituted by the said central cylinder (A.sub.1) and the said peripheral first cylinders (A.sub.4 and A.sub.5) and, the said unit being placed in the water, the joining of any remaining peripheral cylinders (A.sub.2, A.sub.7, A.sub.8) to the said unit (A.sub.1, A.sub.4, A.sub.5).The invention can be advantageously used for the realization of a petrol production platform off coasts.