Convair F2Y Sea Dart

The Sea Dart was Convair's candidate for a 1948 US Navy contest for a supersonic interceptor aircraft. As back in the year there was a lot of skepticism about operating supersonic aircrafts from carrier decks, the US Navy ordered many subsonic fighters. The worry has some foundations as most of supersonic designs of the time required long takeoff rolls, had high speed approach speeds and weren't easy to control, which were all troublesome factors to operate from a carrier.
Therefore, Convair's designer Ernest Stout and his team faced the challenge of putting one of their, back then, most successful designs, the Convair F-102 Delta Dagger on water skis. Their proposal attracted the attention of US Navy's authorities and they were awarded with a contract of two prototypes in late 1951 with twelve further production ones even before the prototype had flown.
The prototypes were to be powered by two afterburning Westinghouse J46-WE-2 turbojets which yielded 6100lbf (27Kn) each with the feds for the intakes mounted high above the wings to avoid ingesting spray. However, as those engines weren't available by the time the prototypes flew, they were powered by two Westinghouse J34-WE-32 which yiekded half of the power.
They were planned to be armed with four 20mm Colt Mk.12 cannons and one battery of folding-fin unguided rockets, however, not any armament was fitted to the prototypes. As the aircrafts in this order were considered as service test vehicles, an additional eight production aircrafts were ordered as well.
It was delta-winged fighter with a watertight hull and twin-retractable hydro-skis for take-off and landing. When stationed or moving slowly in the water, it floated with the trailing edge of the wings touching the water and the skis weren't extended until it reached the speed of around 10mph (16km/h) during the takeoff run.
The prototypes saw two ski configurations. The first of them mounted with just one and the second one mounted with the twin-ski configuration. The first type of configuration proved to be more successful than the second, and the testing of many ski configurations continued until 1957, even after the aircraft was put into storage.
As the US Navy was already losing interest on the type, they considered the type that maybe could fit in the internal arrangement for a submarine aircraft carrier that could carry three of these aircrafts, stored in a chamber that wouldn't protrude from the hull and they would be raised by an elevator just aft of the sail and set to take-off on their own on a smooth sea, but catapulted aft in higher sea. The project didn't go beyond the initial sketches phase as two problems weren't addressed, the hole for the elevator would've seriously weakened the structure and the load of a laden elevator would be hard to transmit to the hull structure.
The first prototype was built at Convair's San Diego, California, facility Lindbergh field and was taken to San Diego bay for testing in November 1952 and shortly later, on 14th January 1953 with E.D. "Sam" Shannon at the controls it made its first unofficial flight while the official one took place in April.
Due to the underpowered engines, the aircraft was sluggish to flight and the hydro-skis weren't as successful as expected as they created violent vibrations during take-off and landing, in spite of the shock absorbing oleo legs they were extended on. The skis were reworked and the vibration problem was partially fixed but the sluggish performance problem persisted on. It wasn't capable of supersonic speed in level flight with the J34 engines and its pre-area rule shape didn't help as it created high transonic drag.
As the results of the first prototype weren't by far the expected, the second prototype was canceled, so the first prototype was modified as a service version fitted with the J46 engines, which performed worse than expected, however, speeds above mach 1 were achieve when flying above shallow waters, making it the only supersonic seaplane up to date.
Unfortunately, on 4th November 1954 it disintegrated in midair over San Diego bay during a demonstration for officials and the press, killing its test pilot, Charles E. Richbourg who was a 31-years old US Navy veteran of the World War II. Although he was quickly rescued from the water, he didn't survive the wounds caused by the airframe breakage.
Even before the accident the Navy had been loosing interest in seaplanes as the problems with supersonic fighters on carrier decks had been overcome and the crash relegated the Sea Dart into experimental status with the subsequent cancelation of all production aircrafts. The three remaining service test examples were completed but the two final ones never flew.
Despite the fact that it was officially retired and had not flown since 1957, at least one F2Y was still in storage in 1962 and, following the Tri-Service Aircraft redesignation system, it was redesignated as Convair YF-7A.

Sources:
1. https://en.wikipedia.org/wiki/Convair_F2Y_Sea_Dart
2. Salamander Books - The Complete Book of Fighters
3. http://www.airvectors.net/avcmast.html