Why do astronauts land in water?

A capsule under parachutes is not gently floating down; it descends fast enough that arrival is a genuine impact. Something has to absorb that energy. Water gives way, spreading the deceleration over a longer moment and over the curved base of the heat shield, which behaves rather like a hull. Coming down on ground instead demands extra hardware — retrorockets, airbags or crushable structure — and every kilogram spent on that is a kilogram not spent on the mission.

The American choice was also geographical. Launches from Florida head east over the Atlantic, so the natural abort and return zones are open water, and in the 1960s the US Navy could place recovery ships almost anywhere. A wide, empty ocean is forgiving about aim, and early guidance was not precise. The Soviet Union launched from the middle of a continent, over land, and built its capsules accordingly: Soyuz descends onto the Kazakh steppe, its fall broken by solid rockets that fire in the final metres and by a seat that collapses under the shock.

There is no single answer any more. Soyuz and China's Shenzhou come down on land; the Space Shuttle landed on a runway like an aircraft, a capability nothing in service has replaced. Crew Dragon returns by parachute to the sea and is lifted aboard a recovery vessel. Boeing's Starliner touches down on desert ground at White Sands, cushioned by airbags. Orion, built to survive the far higher speed of a return from the Moon, splashed down in the Pacific to end the uncrewed Artemis I flight in December 2022, and will do the same with crews aboard.