Taiwan’s Indigenous Defense Submarine Hai Kun (SS-711) Conducts First Submerged Trial

Taiwan’s first Indigenous Defence Submarine (IDS), Hai Kun (SS-711), also known as Narwhal, successfully completed its first submerged sea trials on January 29, 2026.

Earlier, on January 16, CSBC published explanatory materials in Taiwanese Mandarin on its official website outlining the differences between propulsion systems—particularly diesel engines—used on surface vessels and submarines, to help the public better understand submarine technology.

Later, on January 23, CSBC released additional explainer materials covering topics such as the phases and items involved in submarine testing, as well as load planning and safety evaluations, which are part of the preparatory work conducted prior to diving.

On January 28, amid ongoing criticism since the program’s launch, CSBC released additional materials defending the submarine’s development progress, stating that the program remains on track and that costs are lower compared with similar foreign cases involving the development of a new submarine class prototype. The shipbuilder also revealed that the first submerged sea trial would take place on January 29.

Dozens of naval enthusiasts were also seen gathering at Kaohsiung Harbor on the morning of January 29, awaiting the vessel’s departure from the shipyard. According to reports by CNA, supporters held banners and waved the national flag of the Republic of China (ROC) to show their backing for the indigenous submarine program and the navy.

According to CSBC, the functionality of the sonar, propulsion, and underwater log systems was successfully tested during preparatory trials conducted on January 26, 2026. The results will be used as a reference for safety evaluations ahead of submerged operations.

CSBC has been fined by the Taiwanese Navy since December 2025 after missing the deadline to deliver the vessel. Taiwanese media have also reported that CSBC has acknowledged that completing all trials of Hai Kun could take more than one year, based on foreign experience in developing a submarine prototype.

Taiwan’s Current Submarine Force

The Indigenous Defense Submarine (IDS) was unveiled in September 2023 and launched in February 2024. Aside from the advanced—but not yet delivered—Hai Kun, the Republic of China Navy currently operates four submarines.

The more modern and capable force consists of two Chien Lung-class submarines (also known as the Hai Lung or Sea Dragon class): ROCS Hai Lung (Sea Dragon, SS-793) and ROCS Hai Hu (Sea Tiger, SS-794). These boats were acquired from the Netherlands in the 1980s. They are equipped with AEG SUT-264 heavyweight torpedoes produced under license in Indonesia in the 1980s, Harpoon anti-ship missiles purchased from the United States in 2008, and Mk-48 heavyweight torpedoes acquired from the U.S. in 2017.

The remaining two submarines—ROCS Hai Shih (Sea Lion, SS-791) and ROCS Hai Pao (Seal, SS-792)—are significantly older World War II–era platforms transferred from the United States in the 1970s. Both underwent Greater Underwater Propulsion Power Program (GUPPY) conversions and are unofficially referred to in Taiwan as the Guppy class. Despite their age, both submarines remain operational and are reportedly capable of combat duties.