TAIPEI (Taiwan News) — A leaked video that surfaced on the internet on Feb. 8 of a small submarine cruising along the Yangtze River has piqued the curiosity of analysts.

The notably smaller size of the vessel suggests China’s PLA Navy (PLAN) may be diversifying its fleet of underwater vessels and that this mini-sub may have capabilities that traditional models lack, according to a Naval News report.

The sub was geolocated to a spot between Wuhan — which boasts submarine-making shipyards — and Shanghai. Since the facilities at Wuhan only construct conventional subs, there is little chance the vessel is nuclear-powered.

Instead, it could be backed by new lithium-based batteries, per Naval News. Though smaller subs typically cannot voyage as far as larger ones, emergent battery tech could increase their endurance or speed. White stripes are visible along the top of the sub that usually mark a vessel as having been commissioned for the PLAN, as opposed to for export to other countries.

The adoption of smaller subs could signal a new underwater strategy for China, which has accelerated the build-up of its navy in recent years.

Taiwan is also progressing with an indigenous fleet of submarines. Despite Taiwan’s diplomatic isolation, the country has recruited an international team of engineers to participate in the secretive project.

Taiwan’s first submarine may make its maiden voyage as early as next year, but experts have warned of a coming torpedo shortage that may hamper its capabilities. Last year, Turkey scuppered a deal to sell torpedo decoys to Taiwan due to relentless pressure from China.