The French defense ministry invited the media on Friday to observe a facility where it develops submarines and other vessels.
The site in the northern part of the country has one of largest dedicated pools in Europe, measuring 550 meters long and 7 meters deep.
Engineers at the facility use a model submarine to analyze the effect of waves on the hull and observe currents created by the propeller. They say this enables them to build a structure that is as stable as possible, and design the propeller in a way that reduces the risk of detection.
France has territories in the Indo-Pacific, and is increasingly wary of the impact of China's growing maritime presence there on regional security.
France regards Australia as an important partner in the region. So Australia's decision last month to scrap a submarine deal with France in favor of nuclear-powered submarine technology from the United States struck a blow.
French defense ministry spokesperson Herve Grandjean said that the structure of a submarine is critical for stealth and speed. He said France's submarines are the best in the world due to their innovative technology.