It’s believed to be the first time whales have swam into the river and the trio are thought to have taken a wrong turn on their way to Antarctica. Since first being spotted by tourists, two of the whales have managed to swim their way back to the ocean, but there are fears that the third whale, now about 20km downstream, may become stuck on a sandbar. The NT Government has set up a boat exclusion zone, reaching from the rivermouth, 30km upstream to protect both the whale and boaters.  Photo thanks to Parks Australia ‘The last thing we want is a collision between a boat and whale in waters where crocodiles are prevalent and visibility underwater is zero,’ Parks Australia said.