Abstract: A line is deployed along a landing string or along a marine riser of a subsea well. The line has sensors, such as temperature sensors, distributed along its length. In one embodiment, the line comprises a fiber optic line that includes fiber optic temperature sensors distributed along its length. In another embodiment, the line comprises a fiber optic line used to transmit light, wherein the returned back-scatter light is analyzed to provide a temperature profile along the length of the fiber line. The fiber optic line can be deployed by connecting it to the landing string, pumping it down a pre-existing conduit (such as a hydraulic or chemical injection conduit), or pumping it down a dedicated fiber optic specific conduit.