It's a whale of a tale — a bottle-nosed whale swimming up the River Thames past Big Ben and Parliament on Friday as rows of worried Londoners looked on.

The whale was spotted in the afternoon as it flailed around in the murky waters of the Thames, stirring up patches of what looked like blood as seagulls hovered above and rescue boats stood at the ready. It was the first sighting of a Northern bottle-nosed whale in the river since 1913.

Witness Tom Howard-Vyne 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," said Howard-Vyne. "It was an amazing sight."

Other witnesses reported seeing a second whale in another part of the river Friday, and marine experts spotted two disoriented whales off northeastern Scotland last week, suggesting something was causing bottle-nosed whales to become confused.

"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.

A small armada of boats was planning to help the whale late Friday at high tide. One of the boats was equipped with a cradle in case the whale again beached itself. It had already beached itself at least twice Friday, and it was unclear how long it could survive in the river.

Witnesses reported seeing injuries to the whale — which was an estimated 17 feet long — and said its snout was bloodied. Photos also appeared to show damage to one of the whale's eyes and a number of cuts to its torso.

Several onlookers jumped into the 48-degree water, splashing to try to coax the mammal away from shore. Members of the Whale Watch conservation group also ferried across the river to assess its condition.

Bottle-nosed whales normally live in the northern Atlantic, diving deeply and traveling in pods. They can reach 26 feet long — the size of a red double-decker London bus.

When sick, old or injured, whales often get disoriented and swim away from their pod, said Mark Simmonds, science director at Whale and Dolphin Conservation Society.

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 sighting Friday of a second whale in a different part of the Thames, could suggest that something is disrupting the whales, said Laila Sadler, scientific officer at the Royal Society for the Prevention of Cruelty to Animals.

There are many possible reasons whales become disoriented. Scientists have said fluctuating ocean temperatures, predators, lack of food and even sonar from ships can send them into waters that threaten their survival.

Friday's sighting drew hundreds of people and scores of television crews to the river's banks. Television screens carried pictures of the whale for most of the day, captivating Londoners who called radio and television stations asking if they could help.

It was the first time a Northern bottle-nosed whale has been seen in the Thames since the Natural History Museum began recording such sightings in 1913, museum zoologist Richard Sabin said.

He said bootle-nosed whales rarely swim in water as shallow as the Thames, which has an average depth of between 20 and 26 feet.

A minke whale was sighted in the Thames about six years ago, but not as far upstream.

"I am very concerned for the safety of this animal at the moment, particularly if boat traffic increases in the river," said Laila Sadler, scientific officer at the Royal Society for the Prevention of Cruelty to Animals.