LONDON, Jan 20: A small whale swam up the River Thames to central London on Friday, a rare event which drew large crowds of sightseers and brought traffic to a standstill.

But as the whale twice tried to ground itself in the shallow waters, concerns grew that it might not survive.

As the Northern Bottle-nosed Whale beached in front of London’s landmark Battersea Power Station, three men waded into the river hitting the water and then punching the air in celebration as it swam off.

But it soon beached again, prompting more people to jump into the water to move it on.

“It’s unbelievable. I’ve never seen one of those in the wild,” said Liz Downey, education manager at the London Aquarium. “It’s absolutely incredible — it has made our day,” she said.

Police boats tracked the animal as it cautiously circled, moving gradually upstream, and television cameras carried the images live.

Witnesses said it was between five and eight metres in length and that blood was visible in the water.

But experts were divided on what the world’s deepest-diving whale was doing in such shallow waters.

“It can dive to 3,000 metres and stay submerged for an hour,” said Peter Evans of the Sea Watch Foundation. “It will only come into such shallow waters if it is ill. But in doing so it is committing suicide,”

Peter Evans said it was possible the whale had been following fish upstream and had become disorientated.

“Sighting of things like porpoises in the estuary have become more frequent in the past five years — indicating that fish have become more abundant which in turn shows how much cleaner the river is than it used to be,” he said.

The Aquarium’s Downey said it was not an automatic assumption that the whale was so far upstream because it was dying.

“Assessing the health of any animal from that distance is impossible,” she said.

“It’s still breathing and still swimming.”—Reuters