Off the coast of Sinpo is Mayangdo (Mayang island) which is the site of a major Korean People's Army Naval Base. It seems that Sinpo is a hub for the DPRK's naval submarine programme since the naval base is often seen with numerous KPA submarines present in its dock.
Sinpo is an important centre for the fishing industry and other aquacultural related practices. The city is also an important military shipyard; it is believed that the Sinpo-class submarine operated by the Korean People's Army was developed here.
The city's port is not designed for large scale shipping as in other cities such as Chongjin or Rajin, however, the port does have a couple of large piers either for small cargo ships or military vessels.
The Marshal Kim Jong Un guiding the test launch of the Pukkuksong-1
The new ballistic missile submarine being developed at Sinpo
The Pukguksong-1 is a short-range submarine-launched ballistic missile developed by the DPRK, likely in Sinpo. The first test of this missile reportedly occurred in Sinpo in 2014 as part of a land-based ejection test. Since then, the missile underwent a series of tests on land and from underwater test platforms near the city.
In August 2016, the missile was launched on a lofted trajectory from Sinpo as part of a test which proved the de-facto completion of the missile. Since then, new variations of the missile have been developed (Pukguksong 2 & 3), although these were tested in North Pyongan and near Wonsan respectively.
One of the shipyards on the coast of Sinpo is home to a new class of experimental ballistic missile submarines. The vessel was visited by the Marshal Kim Jong Un in July 2019. During this visit, it was reported by the Korean Central News Agency that the vehicle would soon be deployed to operations in the East Sea of Korea (Sea of Japan). It is unknown, at this stage, which ballistic missile systems the submarine is designed to carry.