Here with the two instances since the end of the Second World War [WW2], seaplanes as conceived as AIR SUPERIORITY WARPLANES!
In both cases the designs and aircraft existing only as concepts and prototypes, never reaching the assembly line level of development.
Seaplanes able to take off and land from the water and able as well to engage in the air-to-air combat in the old fashioned manner, mano-a-mano dogfighting!
1. The Convair F2Y Sea Dart.
"The Convair F2Y Sea Dart was a unique American seaplane fighter aircraft that rode on twin hydro-skis for takeoff. It flew only as a prototype, and never entered production, but it is still the only seaplane to exceed the speed of sound."
"The Sea Dart began as Convair's entry to a 1948 U.S. Navy contest for a supersonic interceptor aircraft."
Sea Dart either landing or taking off. I am not sure which one.
"speeds in excess of Mach 1 were attained in a shallow dive with this aircraft, making it the only supersonic seaplane to date. . . . [the prototype however] disintegrated in mid-air over San Diego Bay, California, during a demonstration for Navy officials and the press, killing Convair test pilot Charles E. Richbourg when he inadvertently exceeded the airframe limitations."
Sea Dart in flight. Those "ski-like" devices can be retracted after the warplane becomes airborne?
2. The Saunder-Roe SR./A.1.
Jet powered English flying boat designed in those years immediate after the end of WW2. A flying boat possessing that water-proof hull, again, a project the intent was an air superiority fighter plane.
"The Saunders-Roe SR./A.1 was a prototype flying boat fighter aircraft designed and built by Saunders-Roe. It was tested by the Royal Air Force shortly after World War II."
The SR./A.1 a flying boat with water-proof hull.
The English with their long and successful naval history better than most understanding the advantages of the sea plane?
"In theory, seaplanes were ideally suited to conditions in the Pacific theatre, and could turn any relatively calm area of coast into an airbase. Their main disadvantage came from the way in which the bulk of their floatation gear penalised their performance compared to other fighters."
Other than these two examples the seaplane as an air superiority warplane no other instances exist?
"The bulk of their floatation gear penalised their performance compared to other fighters". This more or less seems to say it all?