Kaohsiung: Taiwan’s first domestically built submarine was spotted undergoing trials at a southern harbor on Saturday, with a source close to the matter confirming to CNA that the tests were part of the final stage of harbor trials before moving on to sea trials.

According to Focus Taiwan, the confirmation came after photojournalists in Kaohsiung captured photographs and video recordings of the Narwhal, Taiwan’s Indigenous Defense Submarine (IDS) prototype, departing from its constructor CSBC Corp., Taiwan’s dock at the Port of Kaohsiung on Saturday afternoon. The IDS prototype was seen navigating the port independently, with over ten technicians aboard its deck.

An unnamed military source told CNA that Saturday’s tests were part of the final stage of the ongoing harbor acceptance tests (HAT). The IDS was conducting power-related system tests, the source added. If all proceeds as planned, the HAT will soon be completed, paving the way for sea acceptance tests (SAT).

Su Tzu-yun, a division director at the Taiwan military-funded think tank Institute for National Defense and Security Research, told CNA that the latest photographs and video clips indicate that the IDS is progressing well and is likely to meet the scheduled November delivery deadline to the Navy. The previous sighting of the Narwhal leaving CSBC’s floating dock in April had the submarine being pulled by a work boat rather than sailing under its own power, Su noted.

The fact that the IDS was now sailing independently suggests that tests have been carried out on its engine, stern, and engineering systems. Video footage also shows that the draft of the submarine prototype, or the depth of the vessel below the waterline, is deeper than during its previous round of tests in April. A deeper draft indicates that all key equipment has been installed with fuel functions operational, signaling the near completion of the HAT and the impending move to SAT.

According to the original timeline set by the Ministry of National Defense, the Narwhal’s SAT was scheduled to begin in April and conclude by September 30 to meet the November delivery deadline. However, media reports have frequently highlighted setbacks in the SAT schedule. Without directly confirming the delay, Defense Minister Wellington Koo told CNA in an interview last month that the SAT for the Narwhal would only commence once all safety requirements are fully satisfied. He also mentioned that there is no definitive schedule for when the SAT will begin.