From Pais's patent application:
It is possible to envision a hybrid aerospace/undersea craft (HAUC), which due to the physical mechanisms enabled with the inertial mass reduction device, can function as a submersible craft capable of extreme underwater speeds (lack of water-skin friction) and enhanced stealth capabilities (non-linear scattering of RF and sonar signals). This hybrid craft would move with great ease through the air/space/water mediums, by being enclosed in a vacuum plasma bubble/sheath, due to the coupled effects of EM field-induced air/water particles repulsion and vacuum energy polarization.
Maybe these are the UFO's the military has been seeing.