A bottom-surface connection installation for at least two undersea pipes resting on the sea bottom, the installation comprising: a first hybrid tower having a vertical riser anchored to a first base and connected to an undersea pipe resting on the sea bottom and having its top end connected to a first float below the surface, and a first connection pipe, preferably a flexible pipe, providing a connection between a floating support and the top end of said riser; and at least one second rigid pipe rising from the sea bottom where it rests or from a second undersea pipe resting on the sea bottom and to which its bottom end that is not anchored to said first base is connected, up to below the surface, where its top end is connected to a second float situated at substantially the same depth as said first float, and fastened to said first float to at least one respective said connection pipe that is flexible and serves to connect it to the same said floating support.