The Rubis was a minelayer submarine derived from the "Saphire" series. She moved 762 tonnes for a length of 66m and 7.12m at the beam. Her motorization was made of two diesels with six cylinders, licensed from Vikers-Armstrong. Each one developed 650hp at 360 rpm propelling her at a maximum speed of 12 knots. During her dives, two electric motors, which developed each 500hp propelled her to a maximum speed of 9 knots. She could be loaded with thirty-two mines of 1090 kg, 3 torpedoes of 550mm and 2 torpedoes of 400mm, 1 canon of 75mm and 2 machineguns of 13mm. Her crew was made up of four officers and forty-one men.

Built since January 1928 at Toulon and launched on the 30th of September 1931, she began her active service in April 1933. Based first at Toulon she got affected to Brest in January 1940. Her first action started on the 1st of Mai 1940 at Dunde and she returned to France only in 1945. The 3rd of July that same year, the British navy launched the "Catapult" operation, where French ships were invested and the crew landed. They where given the choice between joining the French free naval forces or being sent back to France. The crew chose to stay and fight under the commander Muselier. That made the Rubis, the first submarine fighting for a liberated France. During the five years of war, the Rubis scored the deposit of 683 mines, sinking 14 ships and seven dredgers. She also damaged 1 U-boat and sunk 1 ship by torpedoes. She left the active service in 1949 and was scuttled in 1957 as a sonar target.

The Rubis lies perfectly upright on the sand. The bow overlooks the sand at an angle of 45 degrees; the towing cable is still in place hanging down vertically. The deck has vanished used by time, allowing us to see the tanks of compressed air, metal tubes and exterior pumps. The front panel is half open showing its insides. Moving towards the stern, we discover the wells inside which the mines where sunk. All are now empty of course and some have lost their lid. The conning tower as lost its periscopes as well as all other navigational instruments. The stern has been completely cleaned of its propellers, leaving a gaping hole.

There are no particular difficulties, no fishing nets. There can be strong currents and all usual precaution are to be taken on a 40m dive. Nitrox 32 would be the gas of choice for this dive, giving us over 20 minutes without leaving the NDL.