This tranquil beachside enclave normally provides a respite for soldiers, airmen and Marines who come here to relax or to train between dangerous deployments.

But the hotels and bars where military families share laughs in good times became places of shared grief Wednesday as boats and helicopters searched the waters and beachfront for seven marines and four soldiers presumed to have died after a Black Hawk helicopter crashed in dense fog during a routine training exercise.

"My heart is really hurt right now knowing these people were here just on training — knowing they went and left their family members and did not give that goodbye, you know, because they weren't going off to war," a tearful Dolly Edwards said. The 35-year-old wife of a Marine was among hundreds who attended a vigil held at the end of a pier jutting into the Gulf of Mexico on Wednesday night.

The same thick fog that plagued the Black Hawk on Tuesday night engulfed the pier. Combined with the crashing of the Gulf's waves, it created a somber backdrop to the songs, tears and prayers of the large gathering, which included many with strong ties to the military in a part of Florida that is home to the sprawling Eglin Air Force Base.

"We just need to be here to pay respects," said Norman Caron, a retired airman, as he held a candle.

The vigil came after a long and difficult day for searchers who struggled in thick banks of fog to find the remains of the 11 soldiers believed to have been killed in the crash of the UH-60 Black Hawk helicopter.

The military has provided few details about the crash, which happened about 8:30 p.m. Tuesday. The names of the soldiers have not been released.

On Wednesday it was learned that a second helicopter turned back safely shortly before the crash.

Military officials haven't said what caused the crash, but the weather was bad enough for the other crew to return to land, said Maj. Gen. Glenn H. Curtis, adjutant general of the Louisiana National Guard.

Jack Cullen, a National Weather Service meteorologist in Mobile, Alabama, said Thursday would likely bring more dense sea fog and a good chance of rain. He said the foggy conditions could stick around through Friday, a common phenomenon this time of year as warmer southern air encounters cold water near land.

The helicopter that crashed had a veteran crew from Hammond, Louisiana, that served multiple tours in Iraq and helped humanitarian missions after Gulf Coast hurricanes and the BP oil spill.

They were carrying "unconventional warriors" from the Marines Special Operations Command. Like the Army's Green Berets and the Navy's SEALs, they were highly trained to endure grueling conditions and sensitive assignments on land and at sea, from seizing ships to special reconnaissance missions and direct action inside hostile territory.

Tuesday night's training involved practicing "insertion and extraction missions," using small boats and helicopters to get troops into and out of a target site, said Capt. Barry Morris, spokesman for the Marine Corps Special Operations Command at Camp Lejeune, North Carolina.

The helicopter crashed in the Santa Rosa Sound, a strip of water between the mainland of the Florida Panhandle and a long barrier island facing the Gulf. Military officials said search crews were focused on a 6-mile stretch of the sound.

Kim Urr, 62, who works at the Navarre Beach campground near the Eglin Air Force Base training area, said she heard a strange sound, followed by two explosions about 8:30 p.m. Tuesday.

"It sounded like something metal either being hit or falling over, that's what it sounded like. And there were two booms afterward, similar to what you hear with ordnance booms, but more muffled," Urr said.

Human remains were found Wednesday before the weather deteriorated again, and all 11 service members were presumed killed. But it was still considered a search and rescue mission.

All through the day Wednesday, debris from the crash was seen floating in the sound.

"We saw gloves, a uniform with a last name on it," said Alan Collinsworth, a hotel desk clerk. He said that when he got to work at 6:30 a.m. lots of debris was floating by the hotel's waterfront. "We were very shocked."

"It's a big military community here and something like this hits home," said Paul Castillo, a former airman who, along with his 15-year-old son, brought 11 white roses that they laid at a memorial for the crash victims at the pier's entrance. Under his arm he carried a folded American flag.

Earlier in the day, President Barack Obama expressed his condolences to the families and said he is confident a detailed and thorough investigation will take place, said his spokesman, Josh Earnest.

"Our thoughts and prayers are with them and their families as the search and rescue continues," Defense Secretary Ash Carter said on Capitol Hill.

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Associated Press contributors include Lolita C. Baldor in Washington; Jason Dearen in Gainesville, Florida; Freida Frisaro in Miami; Kevin McGill and Stacey Plaisance in Hammond, Louisiana; and Emery P. Dalesio at Camp Lejeune in North Carolina.