A method of cooling a gaseous hydrocarbon stream (10) such as natural gas comprising at least the steps of : (a) sourcing the gaseous hydrocarbon stream (10) in an underwater pipeline (12) to a hydrocarbon facility at sea (18); (b) cooling the gaseous hydrocarbon stream (10) against one or more cooling streams (40) to remove heat from the gaseous hydrocarbon stream (10), and so provide a cooler hydrocarbon stream (20) and one or more warmer cooling streams (30); (c) using the heat of at least one warmer cooling stream (30) to heat the gaseous hydrocarbon stream (10) being sourced in the pipeline (12).