The idea to build a plane that turns into a submarine is not new. However, the mission to build an unmanned variation of such a vehicle is rather 21st-century. Boeing actually already has a design ready.
Earlier this year, the USPTO awarded the aviation giant with a patent for a "rapid deployment air and water vehicle." It's evidently exactly what it sounds like: a drone that can be launched from an aircraft carrier and dive into the ocean near its target. That's when the magic happens. When the drone hits the water, the patent says it detaches portions of the wings with "an explosive bolt or water soluble glue" in order to reduce drag. The drone can then deploy a payload and/or resurface to send messages back to the mothership.
This is not yet a real vehicle. Boeing just has a patent on the design, and it's unclear if the company ever plans to build it. It's basically an invention from a Batman movie, so it's hard to comprehend just how useful it would be in real life. However, people have been trying to build something like this since before World War II, so there's obviously interest. The United States Navy even built and tested a drone that can be launched from underwater. Now let's see if the private sector can do the reverse.