Piaggio designed the P.8 to meet a Regia Marina requirement for a small reconnaissance seaplane that could operate from the large submarineEttore Fieramosca. The aircraft had to be designed so that it could be stowed disassembled in a watertight, cylindrical hangar aboard the submarine. In order to minimize danger to the submarine and the aircraft during flight operations -- which required Ettore Fieramosca to loiter on the surface while the aircraft was being assembled or disassembled -- the aircraft was designed to be assembled quickly for flight operations and disassembled quickly after recovery for stowage in its hangar.
The P.8 was among various small seaplanes considered for use aboard Ettore Fieramosca, which was commissioned in 1930. None of the aircraft were deployed aboard the submarine, and Ettore Fieramosca's hangar was removed in 1931.