Everglades National Park - Wildlife officials prepared to use sound and other herding techniques to try to save pilot whales in danger of stranding in Florida as a glimmer of hope emerged for at least 20 of the animals spotted swimming in life-saving deeper water.Blair Mase, a fisheries stranding co-ordinator for the National Oceanic and Atmospheric Administration, said a Coast Guard helicopter found two pods of whales in about 3.6m of water, "significantly north" of their previous location in Everglades National Park. The short-finned pilot whale is a deep-water species that cannot survive long in the shallows.Another NOAA strandings official, Liz Stratton, said the pod in deeper water could reach as many as 30 animals and that they were about 18km offshore at 12:00 on Thursday."The challenge for them will be to continue to get in the water they are supposed to be in," she said.Mase said about 15 vessels carrying about 35 personnel were en route to find the whales, at least 10 of which have already died since the stranding was discovered on Tuesday. At last count 41 were still alive and swimming, although Mase said it appears none are in the same location as previously and that they are more spread out.Low expectations"The situation is fluid and changing," Mase told reporters.Wildlife workers planned to try using noise such as banging on pipes and revving boat engines to herd the whales out to the open ocean. But Mase cautioned that as in similar past strandings, it is very difficult to move the whales out."We still want to set expectations low because we are facing the same challenges as yesterday. It's quite a distance to deeper water," she said. "Guiding and herding seems to be the best course of action. We're hoping it will just push the whales gently out into the water."Six whales were found dead in the remote area on the park's western edge, and four had to be euthanized. The whales were first spotted on Tuesday about 32km east of where they normally live. It takes more than an hour to reach the spot from the nearest boat ramp and there is no cellphone service, complicating rescue efforts.Teams from NOAA, the National Park Service, the Coast Guard and state wildlife agencies were working to prevent any more whales from stranding. The animals had not been co-operating on Wednesday, when most were in about less than a metre of water.Even if rescuers were able to begin nudging the 41 remaining whales out to sea, they would encounter a series of sandbars and patches of shallow water along the way.The species also is known for its close-knit social groups: If one whale gets stuck or stays behind, the others are likely to stay or even beach themselves as well.Four whales were euthanized Wednesday with sedatives, and more could be put down if their condition deteriorates, Mase said. She described the remaining whales as swimming and mobile but said scientists don't know how long they've been out of the deep, colder water. She said they could be affected by secondary consequences, such as dehydration.Mase confirmed that sharks had begun to feed on the dead whales. Necropsies were being done on Wednesday, and scientists will look for disease or other signs to indicate how whales got stuck in the shallow Everglades waters.