A heat exchanger? In the sea? But of course... Let the sea do the work.

Natural gas can be found under the surface of the earth and below the bottom of the sea. It is rather warm and polluted with sand, water and hydrocarbons. Therefore, before natural gas can be processed, it must be cooled and cleaned. All pollution can be removed at a temperature of approximately -30°C. Air-cooled coolers on land are excellent for this purpose; however, for offshore locations, these are often too expensive. They take up too much space and are too heavy as they require special offshore platforms. Therefore, offshore gas extraction often uses seawater to cool natural gas.