Is Hyundai building a mini-submarine for....?

Hyundai Heavy Industries has begun building a 40 m mini-submarine. The platform may be designed to support inshore surveillance or special forces operations

South Korean shipbuilder Hyundai Heavy Industries (HHI) has begun construction of a mini-submarine for an undisclosed naval customer, the company confirmed to IHS Jane's on 25 September.

The HDS-400 submarine under construction by Hyundai Heavy Industries could be a permutation of the mini-submarine concept known as the KSS 500A unveiled by South Korea's Agency for Defence Development in 2011.

The submarine is based on the company's newly introduced design known as the HDS-400 - a lighter variant of the HDS-500RTN platform that was offered to the Royal Thai Navy earlier in 2015.Displacement 510 tons
Length: 37 meters
Beam: 4.5 meter
Speed: Maximum 20 kt submerged, 5-7 kt cruising
Range 2,000nmi / 21 days, designed to require minimal snorkelling during three-week patrol. 
The endurance is at low speed and severely curtailed at high speed.
Diving Depth 250m
Complement 10 (2 crew with a watch of 5)
Armament: 2 x 533mm (21") heavyweight torpedoes and 4 x 324mm (12.75") lightweight torpedoes.
Torpedo 6 (no reloads on tubes)
Missile/Mine 2 (on payload interface module)
Special forces 7 (combat swimmers = 4)

Up to 14 special forces personnel can embarked. The FPM at the stern allows the deployment of divers, swimmer delivery vehicles and unmanned underwater vehicles.
There is a payload interface module containing two box launchers: one for vertical-launch missiles, the other for mines.