Early in the development of airplanes, the initial design took many inspirations such as the body of a bird because it was seen as the design with the highest probability of success. But we know now that this is not true. So it's quite interesting to see Northrop Grumman taking inspiration from stingrays for their underwater drones that will be used by the United States Military.
Not only is the design similar to a stingray, the name of this drone itself is Manta Ray and it was developed as a project to build an underwater drone that can operate without any human intervention. Manta Ray will be used for spying and patrolling without being detected by the enemy.
It has a standby mode and can sit on the seabed until needed to carry out a given mission. Manta Ray's full specifications are still under wraps. Northrop Grumman simply says it has a modular design to allow it to perform the various missions required.
The development of aerial and ground drones is progressing with them being used in battlefields such as in Ukraine and Syria. Just a few weeks ago Australia showed off the Ghost Shark underwater drone which will perform the same mission as the Manta Ray. America and its allies see the need to monitor China's military in South China Sea waters and autonomous drones are the cheapest short-term solution.