Designed by Gabriel Maugas, it was the first French submarine to be completed with a diesel engine and the only one with four sets of diving planes.

Z was a single-hull design by Gabriel Maugas based on the hull of the all-electric Farfadet-class submarine that was modified to use a diesel engine on the surface and to recharge its batteries.

[1] Based on the experimental engine installed on the canal barge Petit Pierre, it had two vertical cylinder with the flywheel located between them.

When its propellers were delivered, their blades were judged defective, but the navy decided to accept them on 4 January 1904 when the manufacturer offered to lower their price.

[3] The submarine was ordered on the following day to prepare for trials with Aigrette at the Arsenal de Cherbourg and arrived there on 19 July.

[1][7] Gaston Thomson, the Navy Minister, ordered that the testing be repeated and four days of intensive trials were held on 10–15 March 1905, although they were not fully completed until 2 May.

[7] The navy decided to thoroughly refit the submarine on 26 April 1907; this involved repairing the propeller shaft and propellers while replacing the diesel engine with a pair of kerosene-fuelled motor-generators converted by Sautter-Harlé from 120-horsepower (89 kW) diesels intended for the cancelled Guêpe-class submarines.

Other issues that needed to be addressed were that Z had the same thin walls in its internal ballast tanks as the Farfadet-class submarines and these had to be reinforced to prevent their rupture if an intake valve jammed in the open position, as had caused the loss of the submarine Lutin in 1906 and that its batteries needed to be replaced.