JACKSONVILLE, Fla. (AP) —
    On a vessel taking on water and listing to one side, buffeted by 50-foot waves and winds estimated at up to 140 mph, life rafts can be torn apart and lifeboats become impossible to drop into the sea.
    For the crew of the El Faro cargo ship, who trained regularly in calm waters to handle the lifeboats, the situation would quickly have become desperate.
    "Sometimes circumstances overwhelm you. You can do all the planning you want," said Steven Werse, a ship captain and secretary-treasurer of the Master Mates and Pilots Union in Linthicum Heights, Maryland. The union is not affiliated with the El Faro's crew or owners.
    "Without power, the ship is really at the mercy of the sea," Werse said.
    On Monday, four days after the ship vanished, the Coast Guard concluded it sank near the Bahamas in about 15,000 feet of water. One unidentified body in a survival suit was spotted, and the search went on for any trace of the other crew members. The search continued Tuesday.
    A team from the National Transportation Safety Board in Washington was on its way to Jacksonville on Tuesday morning to study the El Faro debris, conduct interviews, and look at documents to find out what went wrong and how to prevent such incidents in the future.
    "It's just a tragic, tragic situation," NTSB Vice Chairman Bella Dinh-Zarr told reporters before departing Washington. Asked whether she was surprised no survivors have yet been found, she said: "We have survival factors as a major part of our investigation."
    Survival suits are designed to help seafarers float and stay warm. But even at a water temperature of 85 degrees, hypothermia can set in quickly, Coast Guard Capt. Mark Fedor said. He noted that the hurricane had winds of about 140 mph and waves topping 50 feet.
    "These are trained mariners. They know how to abandon ship," Fedor said. But "those are challenging conditions to survive."
    The ship, carrying cars and other products, had 28 crew members from the U.S. and five from Poland.
    Coast Guard and Navy planes, helicopters, cutters and tugboats searched across a 300-square-mile expanse of Atlantic Ocean near Crooked Island in the Bahamas, where the ship was last heard from while on its way from Jacksonville, Florida, to Puerto Rico.
    A heavily damaged lifeboat from the El Faro was discovered, with no one aboard, Fedor said. Also spotted were an oil sheen, cargo containers, a partly submerged life raft — the ship carried five rafts, each capable of holding 17 people — life jackets and life rings, authorities said.
    Phil Greene, president and CEO of Tote Services Inc., said the captain had a plan to sail ahead of the hurricane with room to spare.
    Greene said the captain, whose name has not been released, had conferred with the El Faro's sister ship — which was returning to Jacksonville along a similar route — and determined the weather was good enough to go forward.
    "Regrettably he suffered a mechanical problem with his main propulsion system, which left him in the path of the storm," Greene said. "We do not know when his engine problems began to occur, nor the reasons for his engine problems."
    The last message from the ship came Thursday morning, when the captain reported the El Faro was listing slightly at 15 degrees in strong winds and heavy seas. Some water had entered through a hatch that popped open, but the captain told company officials the crew was pumping it out.
    The Coast Guard was unable to fly into the ship's last known position until Sunday, because of the fierce hurricane winds.
    Bernard Ferguson, a commercial fisherman who was at his home on Crooked Island during the hurricane, said it must have been a nightmare for the crew.
    "It's impossible for any kind of vessel to take that kind of beating for that length of time, maybe an hour or two, yes," Ferguson said. "But taking 36 hours of beating, there's no way."
    Anxious family members, gathered at the Seafarers union hall in Jacksonville, tried to remain optimistic, but some wondered why the ship sailed into such a potent storm.
    "What we've all questioned from the very start is why the captain would take them through a hurricane of this magnitude, or any hurricane," said Barry Young, uncle of crew member Shaun Riviera.
    Fedor said the National Transportation Safety Board and Coast Guard will investigate the sinking. The Coast Guard did not immediately release safety records requested by The Associated Press for the ship and its company.