It was Glenn Curtiss' innovative notched Hull that allowed that restrictive drag to finally be overcome (easily seen just aft of the main gear stowed). Note its universal application to modern seaplane design.
@@m3photo726 technically only the DC-3A was, since the DC-3 was originally equipped with Wright R-1820… but since the C-47 was indeed equipped with the P&W, it’s become associated with all DC-3s