It's a whale of a tale -- a bottle-nosed whale swimming up the River Thames past Big Ben and Parliament as rows of worried spectators looked on.
The northern bottle-nosed whale was spotted in central London on Friday afternoon as it flailed around the murky waters of the Thames, stirring up patches of what looked like blood as rescue boats stood on the ready.
"It is a race against time to save the animal," said Alison Shaw, marine and freshwater conservation program manager at the Zoological Society of London.
After dark on Friday, a small armada of rescue boats made frantic searches for the whale, which disappeared from view around 5:30pm after diving under the surface of the water in fading light.
Crews barricaded a section of the river in an attempt to force the animal to change course, but despite glimmers of hope overnight, reports yesterday said the whale was still in central London and did not appear to be making its way back out to sea.
"A whale in the shallow water of the River Thames is like a human lost in the heat of the Sahara desert," said Laila Sadler, scientific officer at the Royal Society for the Prevention of Cruelty to Animals.
She estimated it could survive only for 24 to 48 hours in a river that has an average depth of between 8m and 6m.
"It also seems to be in distress, it has made two seemingly deliberate attempts to beach itself," Sadler said.
Witnesses reported seeing injuries to the mammal, claiming its snout was bloodied.
Photographic evidence also appeared to show damage to one of the whale's eyes and a number of cuts to its torso, though Sadler said these are not uncommon.
The whale -- which is about 5m long -- would normally be seen in the northern Atlantic, diving deeply and traveling in pods. They can reach lengths of 8m.
When sick, old or injured, whales often get disoriented and swim off from their pod, said Mark Simmonds, science director at the Whale and Dolphin Conservation Society, although witnesses reported seeing a second whale in a different section of the river on Friday.
Last week marine officials said they saw two bottle-nosed whales in northeastern Scotland when the mammals are normally seen in northwestern Scotland. That, coupled with the second sighting on Friday, could suggest that something is disrupting the whales, Sadler said.
"It's extremely rare for one to turn up in a river in the United Kingdom. I suspect that the animal may be in ill health," Tony Martin, a senior scientist with the British Antarctic Survey said.
"It's going to be very confused. It's already stranded twice. The poor creature doesn't know where to go," Martin said.
The whale drew hundreds of people and scores of television crews to the river's banks and captivated Londoners who called radio and television stations asking if they could help.
Staff at public relations company Lewis PR, which has offices at Vauxhall Bridge overlooking the Thames, nicknamed the whale Gonzo and launched an Internet blog tracking the animal's progress.
Tom Howard-Vyne, a spokesman for the London Eye -- the world's largest Ferris wheel which is located on the southern bank -- said he saw the mammal swim under Westminster Bridge, near Big Ben.
``I saw it blow. It was a spout of water which sparkled in the air,'' he said. ``It was an amazing sight.''
London's Natural History Museum said it was the first time that a northern bottle-nosed whale has been sighted in the Thames since it began keeping records in 1913.