# South Korea Seohee submarine launch

> Developing situation record from CLSTR: https://clstr.news/situations/south-korea-seohee-submarine-launch
> Updated: 2026-11-05T10:16:11.000Z. Sources: 9. Developments: 2.

The South Korean Navy and the Defense Acquisition Program Administration held a launching ceremony for the Seohee (SS-088) at Hanwha Ocean’s Okpo Shipyard in Geoje. As the second 3,600-ton class submarine in the Jang Bogo-III Batch-II series, the vessel features an expanded 89-meter hull, a hybrid propulsion system combining air-independent propulsion with lithium-ion batteries, and improved combat and sonar systems.

The ceremony included a high-level Greek delegation, including the Greek Ambassador to South Korea and the CEO of ONEX Shipyards & Technologies. This presence highlighted strategic cooperation under Project Trident, a shipbuilding alliance involving the United States, Greece, and South Korea. Following sea trials, the Seohee is scheduled for delivery to the Navy in 2028.

## Claims

- Hanwha Ocean launched the Seo Hui, the second KSS-III Batch-II type submarine for the Republic of Korea Navy. (reported by 3 sources)
- The Seo Hui has a displacement of 3,600 tons. (reported by 3 sources)
- The submarine uses a hybrid propulsion system combining air-independent propulsion (AIP) with lithium-ion batteries. (reported by 3 sources)
- Delivery of the Seo Hui to the Republic of Korea Navy is scheduled for 2028. (reported by 3 sources)
- Project Trident is a shipbuilding alliance between the US, Greece, and South Korea. (reported by 3 sources)
- Hanwha Ocean has built 17 of the 24 submarines ordered by the Republic of Korea Navy. (reported by 3 sources)

## Timeline

### 2026-11-05: Hanwha Ocean launches Seo Hui submarine in South Korea

Hanwha Ocean launched the Seo Hui KSS-III Batch-II submarine in South Korea, marking a milestone for the Project Trident shipbuilding alliance between the US, Greece, and South Korea.

6 sources. https://clstr.news/cluster/hanwha-ocean-launches-seo-hui-submarine-in-south-korea

### 2026-11-03: South Korea launches Seohee, a 3,600-ton advanced diesel submarine

South Korea has launched the Seohee, a 3,600-ton advanced diesel submarine featuring hybrid lithium-ion propulsion and 70 types of localized equipment, slated for delivery in 2028.

3 sources. https://clstr.news/cluster/south-korea-launches-seohee-a-3600-ton-advanced-diesel-submarine

---
Cite as: South Korea Seohee submarine launch. CLSTR, https://clstr.news/situations/south-korea-seohee-submarine-launch