The design was for a
flying boat that would make use of
boundary layer control (BLC) to achieve slow speed flight. It was intended that this would enable the aircraft to land on the open ocean in rough seas and deploy a
dipping sonar. Martin proposed a variant of the P5M Marlin, the P5M-3, to take advantage of this phenomenon. Martin continued development of the P5M-3 under the designation P7M Submaster, introducing two
General Electric J85 BLC gas generators, one in the rear of each outer engine nacelle. A mock-up was built, but the P7M,
Convair XP6Y and
Grumman G-132 were all cancelled when the U.S. Navy abandoned its open-ocean
seaplane requirement. ==Specifications (P7M projected)==