A method for the buoyancy-based installation and/or laying of cables or linear payloads, wherein a) at least one empty tube is laid or provided, the inner diameter of which is greater than the outer diameter of a payload transport tube string; and b) at least one high point head-end station (20, 20a) and at least one low point head-end station will be established or provided in the area of the empty tube run and in this manner accesses to an empty tube system will be provided; and c) at least one active feed system will be provided and at least one payload transport tube string will be pre-installed outside the empty tube, which string fulfills the function of a carrier tube, in which the cable to be laid or the payload to be laid is placed and thus a payload transport tube system is created, which, if it has been closed tightly afterwards, will meet the demand of a low-friction and low-resistance laying thanks to lifting forces in the empty tube that has been flooded with at least one lifting medium; and d) the payload transport tube string will be introduced via the high point head-end station (20, 20a) by means of the active feed system and transported inside the empty tube system to a low point head-end station at the target location and positioned there and for this purpose the empty tube system will be flooded by using at least one primary lifting medium, wherein the outer diameter of the payload transport tube string is adapted to the required and desired effective buoyancy which acts in the lifting medium having a known density upon the payload transport tube string closed for this purpose, in order to counteract the respective weight of the payload transport tube string during the transport and positioning of the payload transport tube string inside the empty tube system, wherein the density of the lifting medium can be modified by additives or replacement and thus the lifting behaviour can be changed also during the installation operation, characterized in that in process step c) at first the predefined length of a cable or a payload will be laid out or composed outside the empty tube for creating the respective payload transport tube string and then afterwards the transport tube lengths will be drawn on the cable in sections and then the transport tube lengths will be tightly connected. a) at least one empty tube is laid or provided, the inner diameter of which is greater than the outer diameter of a payload transport tube string; and b) at least one high point head-end station (20, 20a) and at least one low point head-end station will be established or provided in the area of the empty tube run and in this manner accesses to an empty tube system will be provided; and c) at least one active feed system will be provided and at least one payload transport tube string will be pre-installed outside the empty tube, which string fulfills the function of a carrier tube, in which the cable to be laid or the payload to be laid is placed and thus a payload transport tube system is created, which, if it has been closed tightly afterwards, will meet the demand of a low-friction and low-resistance laying thanks to lifting forces in the empty tube that has been flooded with at least one lifting medium; and d) the payload transport tube string will be introduced via the high point head-end station (20, 20a) by means of the active feed system and transported inside the empty tube system to a low point head-end station at the target location and positioned there and for this purpose the empty tube system will be flooded by using at least one primary lifting medium,