Everglades National Park - Twenty whales believed to be part of a pod found stranded in the Everglades this week were spotted on Friday afternoon moving closer toward shore, a sign they may be reversing their earlier, positive course, wildlife officials said.The whales were about five nautical miles (10km) from the coast, 1.6km closer than on Thursday."I am definitely concerned to hear about their behaviour, that they are less organised, that they seem to be swimming very slowly," National Oceanic and Atmospheric Administration stranding coordinator Blair Mase told reporters. "They may have gotten to the point where they are exhausted."Earlier on Friday, officials had been hopeful the whales were headed back to the deeper, colder waters that form their natural habitat about 32km out to sea. On Thursday, a Coast Guard helicopter spotted three pods of about 35 whales that had moved 9.6km offshore and into water about 5m. "They could dive, they were swimming, and they had a straight shot to their home range," Mase said of the short-finned pilot whales. "And they didn't take it."Mase said the whales' apparent movement inshore raises concerns something may be preventing them from going further out to sea, such as an illness.Eleven of the 51 whales spotted by a fishing guide on Tuesday have died. Six were found dead on Wednesday morning, and four were euthanised. Another died on Thursday.Necropsies on the deceased whales did not reveal any significant initial findings, though they did have empty stomachs, indicating their health may have been compromised. Scientists were awaiting the results of pathology tests to see whether there was any evidence of disease. According to NOAA, pilot whales have been known to carry the morbillivirus, which can cause skin lesions, pneumonia, brain and other infections.A Coast Guard flyover on Friday morning spotted only seven whales. Two others that appeared to be closer to shore turned out to be dolphins, Mase said.The larger group of whales could not be located.But by Friday afternoon, Mase said the seven whales had joined a larger group of 20 heading south and inshore. There is no land in the immediate vicinity for them to beach themselves, she said.On Wednesday, wildlife workers formed a semi-circle around the whales and used anchor chains to bang against their boats and try to herd the whales out of the shallow waters near the remote Everglades beach where they were found. Mase said it was unlikely they would move forward with herding efforts again.More tired"If they're trying to come inshore because that's their natural instinct, and we're pushing them out, we're getting them more and more tired," she said.At some point, "We have to stand back and let nature take its course," she said.From the start, NOAA and National Park Service officials have said the short-finned pilot whales faced significant hurdles. To get to deeper waters they faced a series of sandbanks, tributaries and patches of shallow water that Mase said were "almost like a maze."