Hope of finding four crew members of a fishing vessel found submerged in Nantucket Sound was fading Monday as the Coast Guard continued its search of the frigid waters.

The Coast Guard said rescuers had exhausted all chances to recover the crew of the Lady of Grace a day after the boat was found submerged.

"It is beyond probable, beyond possible that they could still be viable and have survived at this point," Coast Guard Lt. Cmdr. Pat Cook said in a press conference at the fishing hub of New Bedford, 59 miles south of Boston.

The New Bedford fishing vessel was found submerged in 36 feet of water as the Coast Guard on Monday sent a helicopter aloft for a first-light search.

The vessel's lone life raft was found attached to the boat. That raft was the crew's best chance for survival, officials said.

Still, two Coast Guard cutters searched overnight and into Monday morning, using massive search lights and a grid system to scan the ocean surface.

A decision on how long to continue the search would be made sometime Monday, Petty Officer 3rd Class Lauren Downs said.

The Coast Guard also is investigating a report relayed Monday that a boy on a flight Saturday from Hyannis to Nantucket spotted a body floating in the water, Cook said.

Early Monday, Coast Guard officials and New Bedford Mayor Scott Lang met with relatives of the missing mariners and told them the search would be called off.

The 75-foot Lady of Grace was last heard from Friday night and was supposed to return to New Bedford Harbor early Saturday.

In their final words from sea late Friday night, the crew were trying to keep ice buildup from capsizing them in the frigid North Atlantic.

"They thought they were making significant progress on it. They were clearly very cognizant of the fact that they had to return," Lang told the Boston Herald.

Click here to read the Boston Herald story

The boat's last known position was 12 miles south of Hyannis, which is 60 miles southeast of Boston. At the time the boat went missing, the wind was blowing at about 30 to 35 mph with 8- to 10-foot waves.

"Clearly it was extremely cold and icing conditions were severe," Coast Guard spokesman Benjamin Benson said. The boat's trip had been cut in half, to four days, because of the weather.

Searchers spotted an oil sheen on the surface of the water and some small wood chips and debris on Saturday. Officials used underwater cameras and sonar Sunday to detect the sunken fishing boat. Divers later confirmed the find.

According to the Herald, the Coast Guard identified the crew as Capt. Antonio Barroqueiro, 50; Rogerio Vendura, 54; Mario Farinha, 62; and Joao Silva, and said they were in contact with their family members. The Herald identified the last named man as Joao "John" Fidalgo, age 44.

All were presumed dead.

"Even in a survival suit, you can only survive in water that cold for a few hours," Petty Officer Etta Smith said. "This vessel was missing for perhaps as long as since Friday night."

The temperature in the Atlantic Ocean off Cape Cod Monday was 35 degrees.

The Grace had been exchanging e-mails Friday with another fishing vessel, the Lisa Ann II, but abruptly stopped at 10 p.m, the Herald reported. An oil slick and an emergency satellite beacon were the only markers of the boat's watery grave.

"I was hoping for a miracle, but now I can’t hold onto that," Ventura's daughter, Jennifer Patrao, 23, of New Bedford, told the Herald.

Lang told the newspaper the men were well-versed in marine safety, but it was unclear if they had donned their survival suits before all hope for Grace was lost.

Twenty-five individual searches have been conducted since Saturday morning using two Coast Guard cutters, three smaller boats, a Jayhawk Helicopter and a jet from the Cape Cod Air Station. The search has covered 6,000 square miles.

Earlier this month, the Coast Guard had to tow the Lady of Grace after the crew radioed for help, saying they were without power and drifting.

The crew called the Coast Guard early in the morning on Jan. 9 to say they were without power and drifting.

"We've been through this so many times before in the last 150 years," said state Sen. Mark Montigny, D-New Bedford. "At first there's hope and prayers, and then hope begins to fade."

Benson said the Lady of Grace was owned by the Santos Fishing Corp. of New Bedford. There was no phone listing for a company by that name.

The Associated Press contributed to this report.