The flying-underwater thing has never made sense to me. Water, like air, is a fluid so the wings of an intact airplane sinking nose-first, so the theory goes, should generate "lift" and the aircraft could "glide" for a considerable distance from where it sank before reaching the bottom.
Let's try an experiment. Fire up your airplane and climb to whatever altitude suits you. Now shut off the engine, take your hands and feet off the controls, and don't touch the trim. Nothing good will happen. Flying machines remain under control only through human guidance. The Wrights figured that out a long time ago.