Sharpen your pencils boys and girls. DARPA is soliciting proposals for Submersible Aircraft.  Here is the synopsis-

DARPA is soliciting innovative research proposals on the topic of a Submersible Aircraft. In particular, DARPA is interested in a feasibility study and experiments to prove out the possibility of making an aircraft that can maneuver underwater. The proposal needs to outline a conceptual design along with identifying the major technological limitations that need to be overcome in order to maneuver an aircraft underwater. In addition to the conceptual design studies, performers need to outline experiments or computational models that will be used to demonstrate that the major technological limitations can be overcome.

Aircraft are constructed to withstand loads from particular directions arising from the airstream and from dynamic loads imposed on the airframe by accelerated maneuvers. A submersible aircraft must be constructed to withstand additional compressive loads all over the airframe from all directions due to conducting operations in water and at depth.

Perhaps crew chiefs will have to deal with seaweed and barnacles in addition to damage from FOD and birdstrikes. A whole new skill set will arise for naval aviators. Will these craft require anchors and bilge pumps? It is fun to speculate.

It may well be easier to devise a submersible aircraft carrier. I can see it now

Sunset in the north Atlantic. A blood red sun sets over the gray Atlantic rollers. Suddenly, the surface is broken by a large craft abruptly surfacing. The bow rises into the air then splashes to the surface as the large gray ship glides onto the surface at full speed.

Moments later, a hatch on the offset conning tower opens and sailors spill onto the broad flat deck.  Large sections of deck open skyward and elevators lift folded aircraft to the deck. These strange craft are rolled into position while scurrying crews fuel and arm them in the muted red running lights. Curling streams of steam spill to aft from vents on the carrier deck as the vessels screws push it forward.

Elsewhere on deck, sailors mount antenna arrays and open ports revealing defensive weapons. Soon, a fleet of submersible men-of-war have surfaced and set up a defensive perimeter around the submersible aircraft carrier.

After a few minutes, the aircrews run toward the aircraft and strap in. Turbine engines begin to whine as they spool up. Crews disconnect startup carts and run with their equipment to designated locations. As the aircraft power up, their wings unfold and lock into place.

Pilots engage the flapping box and the turbine powered ornithopters begin to flap their articulated wings. The pilot of the lead craft advances the throttle and rolls to the takeoff position while exercising control surfaces. The airboss clears the flight for takeoff and the pilot salutes smartly and advances the thrust to military power.

The black stealth gullwing craft diverts full power to the flapping mechanism and leaps into the air, vanishing into the dark sky.  The vacancy is quickly filled by the next craft. Moments later, another takes wing followed by the rest of the squadron.

At altitude the squadron members meet and assume formation flight. Below, the carrier has already begun to submerge to loiter in position until the appointed time where it will surface and recover the flight if any manage to return. It will be a harrowing night.