Towed streamer marine seismic surveys are conducted using specialist seismic vessels that tow one or more cables known as streamers just below the surface typically between 5-15 metres depending upon the project specification that contain groups of hydrophones (or receiver groups) along their length (see diagram). Modern streamer vessels normally tow multiple streamers astern which can be secured to underwater wings, commonly known as doors or vanes that allow a number of streamers to be towed out wide to the port and starboard side of a vessel. Current streamer towing technology such as seen on the PGS operated Ramform series of vessels built between 2013 and 2017 has pushed the number of streamers up to 24 in total on these vessels. For vessels of this type of capacity, it is not uncommon for a streamer spread across the stern from 'door to door' to be in excess on one nautical mile. The precise configuration of the streamers on any project in terms of streamer length, streamer separation, hydrophone group length and the offset or distance between the source centre and the receivers will be dependent upon the geological area of interest below the sea floor that the client is trying to get data from.