From 6 to 9 December 2022, the Céphée tripartite minehunter (CMT) carried out a seabed monitoring mission in the English Channel.

On the night of December 7, 2022, the CMT Céphée discovered, thanks to its on-board sonars, a historic munition near the port of Cherbourg. This threat was later confirmed by its underwater drone “Self-Propelled Fish”, equipped with a camera.

The 370 mm shell dating from the First World War and containing a load of about 120 kg TNT equivalent, was positioned at a depth of more than 30 meters.

Its countermining was possible, the next day, thanks to the positioning of an explosive charge on the shell by the clearance divers on board in the afternoon. At 4:42 p.m., the Cepheus then triggers the charge installed on the shell, a vibration passes through the bulkheads of the ship, the surface of the water bulges and then gives way to the announcement of the watch leader “against mining performed”. The threat is neutralized, mission successful.

The TMC subsequently continued to clarify this search area before returning to Brest, its base port.