1 of 5 | More than 100 Atlantic white-sided dolphins are stranded in shallow water off Cape Cod, Mass., in what one non-profit animal protection group called the “largest single mass stranding event in our response history.” Photo courtesy of the International Fund for Animal Welfare

Others were stranded in extremely shallow water or were entirely exposed in the mud in an area known as the Great Island at the Herring River.

“Our valiant marine mammal rescue team is in the midst of what may be the largest single mass stranding event in our response history. 125 Atlantic white-sided dolphins stranded this morning in Wellfleet in an area called the Herring River Gut – the epicenter of mass strandings,” the nonprofit International Fund for Animal Welfare said in a statement.

“At leasleast to herd the dolphins back out to deeper waters.”

The group was also using the rising tide to its advantage late Friday as it worked to rescue the animals, which can grow up to 9.2 feet in length and weigh up to 510 pounds.

The large size was making the situation challenging for rescuers.

Estimates put the global population of the Atlantic white-sided dolphins at around 100,000. The species is normally found in warmer parts of the North Atlantic Ocean, according to the U.S. National Marine Fisheries Service.

The name is attributed to a distinctive white stripe on the dolphins’ sides.

In the coastal United States, the dolphins typically roam North Carolina to Maine.

The animals are protected under the Marine Mammal Protection Act.