Taiwan has carried out four shallow-water submerged tests of its indigenous submarine prototype since January 29. These tests mark critical progress for possible delivery to the navy by June. The prototype was developed under Taiwan's Indigenous Defence Submarine programme. Surface navigation tests began last year. Undersea trials and weapons checks were initially set for completion between September and October. Navy delivery was planned for November but delays pushed these timelines back. Due to the delay, opposition lawmakers froze NT$1.8 billion (US$56 million) in funding for follow-up submarines, part of a larger NT$284 billion plan for seven more subs. The opposition said the budget would stay locked until the prototype passed sea trials. Facing this political pressure, CSBC Corporation, Taiwan, the company that built the prototype, started submerged testing on January 29. Following the first test, three more have taken place. CSBC shared the first official video of all four tests on Sunday. These tests are vital for boosting Taiwan's naval defense and countering Beijing's threats with asymmetric warfare capabilities.