Abstract: Longitudinally water-tight cables, such as communication cables, are produced so that the interior of such cables have a filling material containing a water-repellant substance and relatively small diameter gas bubbles embedded in the filling material. The filling material is thickened with a reticulating thixotropic substance having a 3-dimensional network-like structure which is disruptable under mechanical influence and is regenerable over a time span in a motionless state with a significant increase of viscosity. The size of the gas bubbles are adjusted relative to the resistance to disruption of the network-like structure so that the buoyancy of such gas bubbles is significantly below such resistance to disruption in the motionless state of the filling material whereby such gas bubbles are maintained in their respective positions within the filling material in a time-stable manner during a motionless state.