A supersonic jet fighter that was supposed to take off and land on water? Well, that was the idea, anyway, and it worked-to the extent that it did indeed fly off and land on water.
The problem with airplanes is that they need runways, and in wartime, the average runway might as well have the words "Bomb Here" painted on it in big block letters. Runways are among the first targets bombed when a war starts, so over the years people have hatched various schemes to build combat airplanes that don't need a vulnerable stretch of pavement.
The 1950s was an era of aggressive innovation in aircraft design, not all of which was successful. One of the more interesting was the Convair "Sea Dart" hydro-ski fighter. Seaplanes substitute water for concrete, but when the Jet Age came along, seaplanes proved ill-suited to the higher speeds. The Navy's Convair Sea Dart, essentially a jet fighter on water skis, experienced such severe vibration on takeoff that the testing program was scrapped after only five had been built. However, once aloft, the SeaDart handled well.
Convair was a pioneer in exploring the properties of tailless aircraft with delta shaped wings and control surfaces. It might have been a failure as a seaplane, but it contributed a great deal to Canvair's widening database on high performance delta-wing aircraft.