X-Sub buoys by French company Alseamar allow a submarine to receive surface situation data, check its location or communicate without surfacing or raising an antenna.Alseamar designed the X-Sub buoys, now in service with the French Navy, to give a submerged submarine access to additional surface data and to communicate with the outside world without compromising its discretion.The buoy is released from the boat’s Sippican 3” (76mm) ejector while submerged and without changing speed or depth. The buoy floats to the surface and remains connected to the submarine by a 2000m-long copper or fibre-optic cable. With a surface endurance of five to ten minutes, depending on the sub’s speed and depth, the buoy transmits uplink data in real time then scuttles itself once the cable has run out as the sub advances.X-Sub buoys are available in two versions, one with an AIS receiver to fill blanks in the commercial shipping portion of the sub’s tactical situation; the other with a GPS receiver to reset the sub’s inertial navigation systems.In the near future, Alseamar plans new versions with 4000m of fibre-optic cable, hence twice the endurance, offering two-way broadband radio communications, from VLF to the GSM band. These major technological breakthroughs will be of interest to submariners everywhere. More information in Mer et Marine Euronaval 2018 Special issue : "Naval Forces : focus on french technology"