This may be NY Post but the US Navy has published an article that is more sophisticated but is treating the same subject. Both articles below. They caught this on satellite photos.
North Korea may be militarizing dolphins, report says
By Tamar Lapin November 12, 2020
North Korea has repurposed its porpoises — for war, a report said Wednesday.
The hermit kingdom appears to be training dolphins as part of its naval force, according to satellite images obtained by the non-profit United States Naval Institute.
The images show animal pens floating in murky waters, between a shipyard and a coal loading dock, with warships based nearby, the USNI said.