More than 40 pilot whales are shown stranded in shallow water on December 4, 2013 in a remote region of Florida's Everglades National Park, as rescuers race to save them after 11 others from the pod died

Thirty-five pilot whales stranded in a remote part of Florida's Everglades National Park headed toward deeper waters, raising hopes that they could be saved.

Eleven whales have died since the mass stranding was first reported Tuesday after an additional carcass was found. Four of them had to be euthanized.

Another six that went missing overnight Wednesday are feared dead and their bodies may have sunk to the bottom of the ocean floor.

It remains unclear why they strayed into water less than three feet (0.9 meters) deep, in the southern part of the Sunshine State.

"Today we are hopefully more optimistic after a Coast Guard helicopter spotted 35 of the… surviving whales swimming in three separate pods near Plover Key in 18 feet of water this morning," Everglades National Park spokeswoman Mary Plumb told AFP.

"They were in , so they are in better conditions to survive."

Her hopeful outlook was a remarkable development just hours after Blair Mase, of the National Oceanic and Atmospheric Administration, warned of "low" expectations, and said the potential for a successful rescue mission "does not look good."

A rescue team of experts from several agencies, including the National Park Service and the US Coast Guard, grew from 25 to 35 scientists and stranding specialists who can only reach the whales by boat.

But NOAA stressed that the rescuers were treading cautiously as sharks have been seen feeding on the dead whales' carcasses.

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