The successful landing brought an end to a mission that saw the crew capsule fly up to the International Space Station, dock at the floating lab, then drop down to the ground in a fiery landing that confirmed it could one day carry people up to space.
Later this year, the same capsule will carry Nasa astronauts to the space station in a pioneering mission.
The Dragon autonomously undocked from the International Space Station early on Friday. Six hours later, the capsule carrying a test dummy fitted with a host of sensors fell into the Atlantic off the Florida coast.
It marks the first time in 50 years that a capsule designed for astronauts returned from space by falling into the Atlantic. Apollo 9 splashed down near the Bahamas on 13 March, 1969.
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Nasa astronauts have been stuck riding Russian rockets since space shuttles retired eight years ago. It is now counting on SpaceX and Boeing to start launching astronauts this year.
Friday morning’s splashdown was the final hurdle of SpaceX’s six-day test flight.
Minutes earlier, Crew Dragon deployed its four parachutes successfully.
“Everything happened just perfectly, right on time the way that we expected it to,” Benjamin Reed, SpaceX director of crew mission management, said in a live stream from California.
The test mission was a crucial milestone in a government programme that paves the way for SpaceX’s first crewed test flight. The flight is due to take place in July with astronauts Doug Hurley and Bob Behnken.
“This really is an American achievement that spans many generations of Nasa administrators and over a decade of work by the Nasa team,” said Nasa administrator Jim Bridenstine after the splash-down.
Steve Stich, also from Nasa, said: “The vehicle is doing well. The recovery crews are out.”
A boat was ready in the area where Dragon hit the Atlantic and was set to lift our the 16ft spacecraft using a crane. It will reach land with the craft on Sunday.
The first-of-a-kind mission brought 400lbs of test equipment to the space station, including a dummy named Ripley fitted with sensors around its head, neck, and spine to monitor how a flight would feel for a human.
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The space station’s three-member crew greeted the capsule last Sunday, with US astronaut Anne McClain and Canadian astronaut David Saint-Jacques entering Crew Dragon’s cabin to carry out air quality tests and inspections.
Nasa has awarded SpaceX and Boeing Co a total of $6.8bn (£5bn) to build competing rocket and capsule systems to launch astronauts into orbit from American soil, something not possible since the US Space Shuttle was retired from service in 2011.
The launch systems are aimed at ending US reliance on Russian Soyuz rockets for $80m-per-seat rides to the $100bn orbital research laboratory, which flies about 250 miles above earth.
Bridenstine told Reuters the cost per seat on the Boeing or SpaceX systems would be lower than for the shuttle or Soyuz.
Privately owned SpaceX was founded in 2002 by Elon Musk, who is also a co-founder of electric car maker Tesla.
Additional reporting by agencies
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