Abstract: An offshore platform comprises a honeycomb foundation (A), a supporting structure (B) and an above-surface section (C), the foundation and the supporting structure being made of prefabricated reinforced concrete elements which are polyhedral hollow prisms (1, 2) set with gaps (6) between the external faces thereof. The prisms (1, 2) are joined by a system of prestressed vertical and horizontal diaphragm walls (4, 3) formed by pre-tensioning reinforcing bars (7, 8) placed in the gaps (6) between the faces of the prisms (1, 2) and casting-in-situ the gaps (6) later on.