What’s that in the sky? It’s not a bird, or a plane, it’s … a flying submarine?! Meet the Flimmer. That’s short for “flying swimmer,” and comes from the “what will the Naval Research Laboratory dream up next?” category. It’s hard to argue with the logic behind what some have dubbed the “duck drone.” Covering vast distances is far easier in the air than underwater. In addition, an air-delivered unmanned underwater vehicles can operate in areas that lack easy access. Yet the challenges are many, as aerodynamics and hydrodynamics require far different designs. For example, weight is bad for a thin-skinned aircraft,…