French submarine Prométhée (Q153)

Prométhée (Q153) was a French Redoutable class submarine. The submarine sank while on trials near Cap Lévi, off Cherbourg, France, killing 62 men.

Sinking
Eighteen months after her launching, the Prométhée was still on trials before commissioning. She was commanded by lieutenant de vaisseau Amaury Couespel du Mesnil. On 7 July 1932, the crew and engineers from Cherbourg Navy Yard and Le Creusot ironworks ran trials of the engines on the surface.

About noon, the electrical engines trial was over. the Prométhée was seven nautical miles north off the Cap Lévi's lighthouse, in Fermanville. The captain ordered to begin the diesel engines trial. At that moment, the ballast tanks flooded without any apparent reason. The submarine sank immediately but was not yet fitted for diving: compressed air tanks were empty so blowing out the ballast was impossible and no oxygen tanks were functional. About 15 people were on the Prométhée' deck, including Couespel du Mesnil. He reported his submarine started to sink by the aft faster and faster, making an angle of 80°. The whole process lasted less than a minute.

Rescue attempts
Seven men out of 15 had survived at sea for an hour, when a fishing boat rescued them. Intensive searching began in the afternoon to find the wreck, as soon as the loss of the Prométhée is known at Cherbourg. International help was soon organized. The Italian ships Artiglio and Rostro, world-known for their diving skills, were asked to come.

Patrol boats and sea planes crisscrossed the area. The next morning, aviso Ailette spotted the telephonic buoy of the submarine. Several calls were made but no answer returned. On 9 July, the Artiglio and the Rostro arrived in the area and atmospheric divers reached the wreck, 75 meters below the surface. They knocked on the hull but didn't get any answer. Forty-eight hours after the accident, the crew was assumed dead.

It was impossible to raise the submarine so it was impossible to give the bodies back to their families and to understand what happened. Based upon the Lieutenant Couespel du Mesnil's testimony, the investigating committee assumed that the ballasts flooding was due to a short circuit or an error in wiring.

Posterity
The loss of the Prométhée had a huge emotional impact in France and much of the rest Europe as well. Bastille Day ceremonies were cancelled in several cities, such as Cherbourg. On the 30 July 1932, Prime Minister Édouard Herriot and Minister of Marine Georges Leygues paid tribute to the victims and their families. A cross was erected in Fermanville in their memory.

A street in Dunkerque is named after the Prométhée.