TOULOUSE, France (AP) — Once again, the oceans beckon for France’s veteran nuclear-powered attack submarines.

The Associated Press got rare access aboard a French navy Rubis-class submarine as it was being readied for another mission in sprawling naval dockyards in the Mediterranean port of Toulon.

France’s fleets of nuclear-powered submarines are shrouded in secrecy. The French military would not allow this submarine to be identified by name. A naval security officer scrutinized all the images AP journalists took aboard the vessel and asked that some be deleted or cropped to avoid showing submarine technology and security measures at the docks.

Aboard the cramped vessel, submariners crammed into the confines of a small compartment and carried out maintenance work. Others loaded supplies aboard, carrying boxes down narrow gangways. In the control room, crew members hung strips of lights amid the spaghetti of cabling and equipment.