Propelled on the surface by two diesel engines producing a combined 6,000 horsepower (4,474 kW), they had a maximum speed of 18.6 knots (34.4 km/h; 21.4 mph).

Laid down at Chantiers Dubigeon in Nantes, France, on 5 November 1928 with the hull number Q157, Phénix was launched on 12 April 1930.

[2] On 15 December 1938, the two submarines anchored for the night off Cap Saint-Jacques on the coast of Cochinchina, the southern portion of French Indochina.

During their stay there, Italy invaded Albania on 7 April 1939, and they received orders to prepare for possible combat operations against Italian forces.

[2] A Loire 130 flying boat of Escadrille 5 based at Cat-Laï that was participating in the maneuvers reported that it had sighted Phénix on the surface on the horizon at 10:07 and was approaching her at 10:22.

[2] When the news reached the French Commander-in-Chief of the Naval Forces in the Far East, Squadron Vice-Admiral Jean Decoux, at 15:00, he ordered Lamotte-Picquet to get back underway and return to the area to join the search.

[2] Lamotte-Picquet reached the scene at 16:35, and she and L'Espoir searched until 17:06, finding only a slick of diesel oil which had appeared on the surface in the area in which Phénix had disappeared.

[2][4] With Decoux aboard, L'Espoir put back to sea that morning and joined Lamotte-Picquet, the aviso Marne, and the survey ship Octant in the search.

Strong currents interfered with the search,[5] but during the morning, a Loire 130 flying boat of Escadrille 5 took advantage of favorable lighting conditions to spot Phénix′s wreck, which was 12 nautical miles (22 km; 14 mi) northeast of the island of Hon Chut, 11.7 nautical miles (21.7 km; 13.5 mi) bearing 53 degrees from Hon-Chut Light.

[4] Salvage activities began on 22 June 1939 with several efforts to place a chain around Phénix′s hull so that it could be towed into shallower water where divers could reach it.

On 28 June 1939, the United States Asiatic Fleet submarine rescue vessel USS Pigeon (ASR-6) arrived on the scene, but salvage work had succeeded only in towing Phénix′s wreck to a depth of 95 metres (312 ft), too deep for Pigeon′s divers to reach.

However, the investigation concluded on 19 July 1939 with the determination that the most probable cause of her loss was an explosion that occurred when Phénix′s batteries released hydrogen gas due to Phénix′s poor material condition, and that the explosion had killed or incapacitated the officers and men in her control room, rendering them incapable of carrying out the maneuvers necessary to save Phénix.

[3] In an op-ed published in the New York Times on 17 June 1939, United States Navy Reserve Commander Edward Ellsberg debunked the sabotage conspiracy theory, citing the improbability of a foreign agent being assigned to a submarine crew or of a saboteur gaining unobserved access during a visit to a submarine in port.

[10] In March 1941, the crews of Phénix′s sister ships Monge and Pégase held a memorial service over the site of the wreck of Phénix.