A bottom-to-surface connection device comprising at least one undersea pipe or riser (1, 1a-1b) including at least one float and possibly including only one float (2, 2 1 -2 7), said float being connected at its bottom end to a junction device creating a leaktight flexible joint between the bottom end of the float and said riser, characterized in that the bottom-to-surface connection device comprises said junction device which is interposed between and secured to a bottom portion of the riser going down to the sea bottom and a top portion of the riser passing through said float and rising to the surface, said junction device comprising at least: - a first forged body of revolution secured to the top end of said bottom portion of the riser, and forming an internal tubular duct section (22 3) having substantially the same diameter as said bottom portion of the riser; and - a second forged body of revolution secured to the bottom end of said top portion of the riser, and forming an internal tubular duct section (24 4) having substantially the same diameter as said top portion of the riser; - said first and second forged bodies (22, 24) being interconnected in flexible and leaktight manner by at least a first flange in the form of a body of revolution secured in leaktight and reversible manner to said second forged body and connected to said first forged body by at least a first laminated abutment in the form of a body of revolution, comprising a plurality of elastomer layers interposed between rigid reinforcements preferably made of metal defining surfaces of revolution having the same axis as the common longitudinal axis of revolution ZZ' of said first and second forged bodies (22, 24) and said first flange (23, 23a-23b), said surfaces of revolution being frustoconical in shape or skew surfaces, such as surfaces of sections that are ellipsoidal or parabolic or hyperbolic or preferably spherical in shape. - a first forged body of revolution secured to the top end of said bottom portion of the riser, and forming an internal tubular duct section (22 3) having substantially the same diameter as said bottom portion of the riser; and - a second forged body of revolution secured to the bottom end of said top portion of the riser, and forming an internal tubular duct section (24 4) having substantially the same diameter as said top portion of the riser; - said first and second forged bodies (22, 24) being interconnected in flexible and leaktight manner by at least a first flange in the form of a body of revolution secured in leaktight and reversible manner to said second forged body and connected to said first forged body by at least a first laminated abutment in the form of a body of revolution, comprising a plurality of elastomer layers interposed between rigid reinforcements preferably made of metal defining surfaces of revolution having the same axis as the common longitudinal axis of revolution ZZ' of said first and second forged bodies (22, 24) and said first flange (23, 23a-23b), said surfaces of revolution being frustoconical in shape or skew surfaces, such as surfaces of sections that are ellipsoidal or parabolic or hyperbolic or preferably spherical in shape.