H I Sutton - Covert Shores

Flag Operating under great secrecy, photos of the North Korean made ‘YUGO Class’ midget submarines operated by the Vietnamese Navy are very rare. Two YUGO Class midget submarines supplied in 1997 and are operated by submarine unit M96. The deal included 16 torpedoes, 282 batteries and 8 mines. Although the torpedo type is not reported they are known to be of 1960s Soviet type, probably Type 53-56 rather than the more recent CHT-02D type. Not all of the equipment sold (torpedoes, batteries, mines) was new and Vietnam had to replace it with Russian source units.
North Korean Yugo submarine
Although the image only shows the upper surfaces, the outer doors of the twin 533mm (21”) torpedo tubes are clearly visible in the nose. The yellow object is a distress / communication buoy. The hatch halfway along the forward casing is for a diver lock-out chamber.

Previous photos (below), collaborated by satellite imagery, were adequate to allow identify the type of submarine, but were otherwise of limited use.
North Korean Yugo submarine

The Vietnamese operated submarine is essentially similar to the P-4 YUGO boat captured by South Korea during an infiltration mission in 1998 and subsequently put into service with the South Korean Navy. It was recently taken out of service and put on public display at the war memorial. Interestingly the sensors of the captured boat, including the sonar, were of Japanese origin.
North Korean Yugo submarine