JACKSONVILLE, Fla. — 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.