TAIPEI (Taiwan News) – Taiwan’s first indigenous submarine headed back to dock Friday for adjustments ahead of a trial phase likely to include diving below the surface.

The Narwhal conducted two consecutive days of sea acceptance tests Nov. 27-28. However, it did not start the next phase of the trials to include shallow diving.

Shipbuilder CSBC Corporation Taiwan emphasized that the tests were being managed by a professional team putting safety first, the Liberty Times reported. Friday’s tasks included adding equipment, improving watertight conditions, and preparing the submarine for underwater warfare.

Last month’s round of tests involved the periscope, sonar, navigation equipment, engine power, and communications. After shallow diving, the final phase should be diving to greater depths.

According to the original timetable, the sea acceptance tests should have ended in September, with the Navy taking delivery of the Narwhal in November. According to the contract with CSBC, the company could be fined NT$190,000 (US$6,000) per day if it fails to meet the agreed deadlines.