Lockheed CL-130 HOW, Hercules-On-Water amphibian
In 1968 Lockheed set to work modifying the C130 to become an amphibious flying boat. The modification would involve a redesigned nose, the addition of a boat hull directly to the standard C130 hull, changing the engine mountings to Electra-style over wing cowlings, and addition of a hydro-ski to the lower keel to allow operation onto sea-state 7 (!) conditions in a similar manner to a hydrofoil.
A 1/16th scale flying model was commissioned to test the concept. The design eventually progressed to increasing the vertical tail surfaces and dorsal fin and addition of horsal fins to increase extreme low-speed handling - both features carried forward onto Hercules STOL projects.
Unfortunately insufficient military or civil interest led to the promising project being abandoned.