China says Jiaolong deep-sea submersible will head thousands of meters underwater for its first dive attempt on Thursday.

The first go will take the world’s first state-owned manned submersible at least 5,000 meters underwater in Mariannas Trench in the West Pacific Ocea, may further, pending weather conditions. The submersible is undergoing internal checks ahead of its attempt, having been delayed this week due to weather and sea conditions.

Three submariners will go down with the vessel on Thursday. The Jiaolong is designed to reach depths of 7,000 meters below sea level. It has succeeded in diving nearly 5,200 meters deep in the Pacific Ocean last summer, and will attempt to break its own record this week.