A tower of the multi-riser hybrid type, the tower comprising: a) a vertical tension leg secured at its top end to a carrier structure suitable for being suspended from a float, referred to as a "top" float, that is immersed in the subsurface, suspension preferably being via a chain or cable, said tension leg being secured at its bottom end to a bottom guide structure and being suitable for being fastened to a base member resting on the sea bed or to a foundation anchor that is preferably of the suction anchor type embedded in the sea bottom, the bottom end connection preferably being via a flexible joint; b) a plurality of rigid vertical pipes (3-1, 3-2) known as risers, the top end of each pipe or riser being secured to said carrier structure, the bottom end of each said rigid pipe or riser being suitable for being connected to an undersea pipe (2-1, 2-2) resting on the sea bottom, the connection preferably being via automatic connectors between said bottom ends of the risers and the ends of the undersea pipes (2-1, 2-2), and preferably via bent sleeves and/or junction pipes; c) a plurality of guide means for guiding said risers, said guide means and said bottom guide structure being suitable for maintaining said risers arranged around said tension leg, preferably being distributed regularly and symmetrically around said tension leg; and d) buoyancy elements co-operating with said tension leg, the buoyancy elements being distributed along said tension leg, and preferably being constituted by buoyancy elements that withstand undersea hydrostatic pressure, and more preferably being syntactic foam buoyancy elements; and e) said tower comprises a plurality of buoyancy and guide modules (20, 20-1, 20-n) constituting a plurality of independent structures suitable for sliding along said risers, said structure supporting said buoyancy elements and guiding said risers in a preferably regularly and symmetrically distributed position around said tension leg, characterized in that said independent structures constituting said buoyancy and guide modules (20, 20-1, 20-n) are suitable for sliding along said tension leg. a) a vertical tension leg secured at its top end to a carrier structure suitable for being suspended from a float, referred to as a "top" float, that is immersed in the subsurface, suspension preferably being via a chain or cable, said tension leg being secured at its bottom end to a bottom guide structure and being suitable for being fastened to a base member resting on the sea bed or to a foundation anchor that is preferably of the suction anchor type embedded in the sea bottom, the bottom end connection preferably being via a flexible joint; b) a plurality of rigid vertical pipes (3-1, 3-2) known as risers, the top end of each pipe or riser being secured to said carrier structure, the bottom end of each said rigid pipe or riser being suitable for being connected to an undersea pipe (2-1, 2-2) resting on the sea bottom, the connection preferably being via automatic connectors between said bottom ends of the risers and the ends of the undersea pipes (2-1, 2-2), and preferably via bent sleeves and/or junction pipes; c) a plurality of guide means for guiding said risers, said guide means and said bottom guide structure being suitable for maintaining said risers arranged around said tension leg, preferably being distributed regularly and symmetrically around said tension leg; and d) buoyancy elements co-operating with said tension leg, the buoyancy elements being distributed along said tension leg, and preferably being constituted by buoyancy elements that withstand undersea hydrostatic pressure, and more preferably being syntactic foam buoyancy elements; and e) said tower comprises a plurality of buoyancy and guide modules (20, 20-1, 20-n) constituting a plurality of independent structures suitable for sliding along said risers, said structure supporting said buoyancy elements and guiding said risers in a preferably regularly and symmetrically distributed position around said tension leg,