Abstract: An encasing method and apparatus in which an external casing, has an insulating, tubular liner therewithin, and one or more pipes or electrical cable are located within the liner. The liner and pipe or cable are floated into the casing after the casing has been flooded with water or other flotation liquid, following the laying of the casing on a support surface, such as the ground or a seabed. After installation of the liner and pipe or cable, water continuously flows through the casing and through the liner, whereby dissipation of waste heat can be controlled by controlling the velocity of flow of the water through the casing. The pipe or cable can be floated out of the liner for repair or replacement without removing or modifying the casing or the liner. Moreover, leaks in the pipe or cable can be monitored on a continuous basis, such as by using a gas chromatograph.