There are two fundamental dichotomies in spacecraft design (or three, if you count the types of fuels used for their rockets). You have ballistic capsules in opposition to winged craft/lifting bodies, and you have water landings as opposed to coming in on solid ground. Three of the four possible combinations have been used by crewed spacecraft but one hasn’t: a water landing of a winged vehicle.
That’s not to say it hasn’t been examined, though. NASA studied the ramifactions of an emergency ditching of a Shuttle Orbiter (conclusion: a lot of damage to the underside, but it would stay afloat for a while as long as the wings weren’t badly holed), and the Australians famously photographed the USSR retrieving a BOR-4 test article from the Indian Ocean in 1983. Even earlier, the American ASSET, originally conceived for testing the alloys earmarked for the X-20’s heat shield, splashed down off Ascension Island after a suborbital jaunt from Cape Canaveral.
As far back as 1959, NASA was testing the concept using a water tank at Langley Research Center in Virginia. They had a chicken-and-egg problem, though. How do you build a water-landing spacecraft without tests to tell you what it will look like? But then how do you do the necessary tests without having it built first? Ultimately they had to just go ahead and build it based on first principles and common sense. What they came up with never had a name, so for convenience’s sake we’ll call it the Langley Water Lander.
The re-entry vehicle they posited was a light one, just 3600 pounds (1.6 tonnes), which is only a few hundred pounds more than a Mercuty capsule. Given that much of it was wings, it would have definitely seated only one astronaut, perched in a slim fuselage.
And it really was a lot of wing for its size, 27 feet from tip to tip and with an area of 263 square feet (7.0 meters and 24.4 square meters); it had no tail at all, though it did have a large vertical fin. The wing was gently curved, making a cross-section something like a boat so that the craft could rock from side to side on the surface of the water without the tips of the wings dipping below the surface. This was made even more unlikely by the fact that the wingtips were designed to fold up once the craft had gone subsonic.
On its underside were two retractable 4.7-foot × 0.67-foot (1.4m × 0.20m) water skis and a smaller triangular skid aft, roughly a foot to a side, for drag; this was found to be more stable during the final run-out than anything involving a single nose ski.
Thus configured, a one-eighth scale model was built and tested, with the conclusion that the landings were not so bad at all. The Water Lander wasn’t too sensitive to a little yaw in the touch-down, and even with small waves (eight inches high and fifty feet long, or 20 cm and 20 meters,to scale) the run-out was only three to four hundred feet with a maximum of 5.1 g deceleration. On smooth waters, it came in at under 3.0 g and 100 feet further travel after touchdown.
The Water Lander was never intended to be built for actual use, but rather was a reflection of where NASA was in late 1959. They examined a great many basic possibilities for the crewed space program, many of which have fallen into obscurity. In the case of winged water landers, the reason likely was that there’s no advantage to them. A ballistic capsule, almost uncontrolled, can benefit from a target as big as the South Pacific Ocean. But the whole point of a winged re-entry vehicle is that it can be directed once in the atmosphere, and if you can do that you might was well direct it towards a runway.
Model Investigations of Water Landings of a Winged Reentry Configuration having Ourboard Folding Wing Panels, William W. Petynia. Langley Research Center. December 1959.