Two American astronauts were greeted by a group of private boats on Sunday as their SpaceX capsule splashed down safely in the Gulf of Mexico, an encroachment that distracted from an otherwise triumphant milestone for the country’s resurgent space program.
More than a dozen boats converged on the singed Crew Dragon pod, which NASA officials said had withstood temperatures of up to 3,500 degrees during its re-entry into the Earth’s atmosphere.
A few of the vessels went in for a closer look at the capsule, which, aided by parachutes, gently hit the water off the coast of Florida.
As the capsule bobbed in the water, a recovery team instructed the boaters to stay away.
The episode raised concerns among NASA and SpaceX officials about security and safety procedures, including whether to share details about the splashdown area with boaters ahead of time.
If there had been an emergency, NASA officials said, the private boats might have impeded recovery efforts. They added that there could have been poisonous fumes from the capsule that posed a risk to the boaters.
The NASA administrator, Jim Bridenstine, acknowledged that the unauthorized reception should not have happened.
“I think all of America was very anxious to see the capsule land in the water, but yeah, it’s something we need to do better next time,” Mr. Bridenstine said during a news conference after the astronauts’ safe return.
A Coast Guard spokesman said on Sunday that an 87-foot patrol boat was deployed to the area four hours before the splashdown to try to discourage boaters from approaching the capsule. A 45-foot response boat was also sent there.
The Coast Guard warned boaters to stay clear of the area in a radio broadcast two hours before the splashdown, said the spokesman, Petty Officer Third Class John Michelli.
“With limited assets available and with no formal authority to establish zones that would stop boaters from entering the area,” he said, “numerous boaters ignored the Coast Guard crews’ requests and decided to encroach the area, putting themselves and those involved in the operation in potential danger.”
He said the Coast Guard would conduct a review of the operation in cooperation with NASA and SpaceX.
“The actions of those boaters today were not representative of the average boating community, and they put themselves and others at risk through their actions,” Petty Officer Michelli said. “This lack of regard for safety is something that the Coast Guard takes very seriously.”
One of the boats flew a Trump campaign flag, a NASA broadcast of the capsule’s landing showed. A spokesman for President Trump’s campaign said it was not connected to the display.
NASA officials said that an area of 10 nautical miles was cleared for the spacecraft’s return, and that private boats converged on the capsule once it was in the water.
“I mean, that capsule was in the water for a good period of time and the boats just made a beeline for it,” Mr. Bridenstine said. “So it’s a big area to have to clear, and to clear all of it is probably going to require more resources.”
Robert L. Behnken and Douglas G. Hurley, the NASA astronauts, returned to Earth after nearly 64 days in orbit, most of them spent aboard the International Space Station.
Their trip home was aboard the Crew Dragon, a capsule built by the private company SpaceX to transport NASA astronauts. The agency has relied on Russia for trips to space since the space shuttles were retired in 2011.
While the shuttles, like airplanes, landed on runways, SpaceX opted for water landings, which NASA had not done since 1975, when the last of the Apollo modules went to space.
Gwynne Shotwell, president and chief operating officer of SpaceX, said during the news conference that the episode was a learning experience.
“The lesson learned here is that we probably need more Coast Guard assets, maybe more SpaceX and NASA assets as well,” Ms. Shotwell said. “What’s important is that Bob and Doug got safely on the boat. We were able to keep the area clear for landing and then asked people to move back as they came a little too close to the Dragon capsule, which they did.”
NASA and SpaceX identified seven sites along the Florida coast for the splashdown on Sunday, and chose one near Pensacola because it was farthest from Tropical Storm Isaias, which mostly spared the state significant damage over the weekend.
Marie Fazio, William Lamb and Michael Roston contributed reporting.