There are two theories on what is behind the stranding. One is sickness.

The second is possible U.S. Navy sonar exercises off the Keys last week that might have disoriented the dolphins, who are keenly attuned to sound and communicate with each other with sound.

Navy officials said an investigation is under way.

In the meantime, surviving dolphins are struggling to pull through.

"Many people are in the water with the animals," said Lloyd Brown, of the Marine Mammal Conservancy. "Some of these animals are in such bad condition that they need to be physically held up so they can breathe."

Dolphin caretakers are in desperate need of more volunteers and are asking for donations.

More than 60 rough-tooth dolphins beached Wednesday in just a few inches of water on flats and sandbars about a quarter mile off Marathon, about 45 miles east of Key West. More than 20 of them have died or been euthanized.

Officials from one of three rehabilitation centers aiding the dolphins asked for more volunteers Sunday.

"Some of the animals are in such bad condition they need to be physically held up so they can breathe," said Lloyd Brown, vice president of the Marine Mammal Conservancy in Key Largo.

As of Sunday afternoon, the Conservancy was caring for 26 dolphins. Brown said the center also needs food and water for volunteers and money for dolphin food and medication.

"This will be one of the largest efforts ever made on rehabilitation of stranded mammals in history," said Robert Lingenfelser, president of the Conservancy. "This is a major effort on a little nonprofit that's all-volunteer."