(CNN) -- Six short-finned pilot whales have died and about 45 other whales were trapped Wednesday in shallow water off Florida's Everglades National Park.
Wildlife officials were trying to rescue the whales, which were found Tuesday stranded on the park's remote Highland Beach or trapped nearby in shallow water, Everglades park spokeswoman Linda Friar said.
Rangers found an unspecified number of whales beached, and others in the shallow water, after a fishing guide reported seeing one of the whales Tuesday afternoon, Friar said.
Wildlife workers were able to get some of the beached whales back into the water, she said.
The whales are believed to have approached the beach at high tide, but were unable to leave when the tide dropped, she said.
On Wednesday, they were stranded in "miles and miles" of shallow water, said Blair Mase, a marine mammal scientist with the National Oceanic and Atmospheric Administration. Officials were prepared to euthanize them, if needed, but were simply observing them, she said.
In all, 25 people were involved in rescue efforts, including officials from NOAA, the Marine Mammal Conservatory and the Marine Mammal Rescue Society, Mase said.
Fishermen spotted the whales, several of which had beached themselves, on Tuesday night in a remote area accessible only by boat off the west coast of the Everglades.
Such strandings are common and occur in a variety of locations, said Phillip Clapham, director of the whale research program at the National Marine Laboratory in Seattle, Washington.
While it's difficult to explain why any particular mass stranding occurs, they tend to occur in areas where previous strandings have occurred, during low tide -- particularly those around the new and full moons, in areas dotted with sand bars and during storms.
The animals' cohesion can doom an entire group. "These are very, very social animals," Clapham said in a telephone interview. "They remain together as family units. If the lead animal gets in trouble, probably everyone else is going to follow them and be in trouble."
Would-be rescuers have their hands full, he said, noting that the animals can weigh a ton apiece. "It's a largely, but not entirely, hopeless undertaking," he said.
Clapham noted that on Cape Cod in Massachusetts, where such strandings are routine events, rescuers have used cranes and a flatbed truck. But heavy equipment is not readily available in the remote area off the Everglades where the stranding occurred.
No good estimates exist for how many pilot whales exist, but they are not endangered, he said.
"These events, while they're tragic, don't have any implications for the survival of the species."
CNN's John Zarrella contributed to this report