Australian officials say they will try to guide a hump whale from a crocodile-infected river in the northern region, as it got lost and ended 30 km (18.5 mi) inland.
Whales and others were on an annual sea migration when some of them “took a wrong turn”, experts believe.
Two whales were later able to swim out of the river, but at least one remains.
This is the first known example of a whale found in the crocodile region so far in Australia.
Given its estimated 16 m (52 ft) length, the crocodile is unlikely to be disturbed by the crocodile.
Officials said on Monday that the risk could increase if whales were trapped in shallow water.
Wait, what happened?
People were spotted in the East Alligator River last week at Kakadu National Park – Australia’s largest national park and a World Heritage-listed site.
The sight of the animals bending from the mud of the river – so far from the open water – surprised the locals.
“This is something that has never been recorded before – not only in the Northern Territory – but [in] Australia. This is really unusual, ”said Carole Palmer, a marine ecosystem scientist for the region’s government.
He said it is difficult to determine whether more than one whale needs assistance due to the “gray-gray waters” of the river.
How did the whale get there?
Ms Palmer told the Australian Broadcasting Corporation that experts were not sure why “these whales took the wrong way off the country’s northern coast”.
It is believed that they were heading south from Antarctica, but accidentally entered a estuary, which moved them further up the river system.
Whales migrate to warm water during spring to give birth before heading back to Antarctica to warm Australia’s waters.
Whale migration: rare encounter on the Great Barrier Reef
What is the danger?
Although the river is inhabited with saltwater crocodiles, experts do not expect a collision.
But if the whale gets stuck in the shallows and rot in a bank, “it’s an easy feed for them,” Ms. Palmer told ABC.
“There is no way we can pick up the 12-16m humpback whale from the sandbar and possibly when the croc kick kills.”
What are the officials doing to help?
Boats have been banned along the river to clear a path to the sea.
It was expected that the whale would pass on its own, but it remained around the deepest part of the river – about 20 km from the sea.
Ms. Palmer said officials were considering several options to get it out, such as using a “noisy sound” from nearby boats or recording humpback whale calls.
“It’s difficult on every level, but everyone is really trying to get on with this in the most positive way,” she said.