The Zoological Society of London (ZSL) reported that the River Thames, which was once considered one of the most polluted and congested waterways in the world, is now populated by a number of large marine mammals.
Animal conservationists from the ZSL studied documented sightings of 2,732 marine animals in the river over a ten year period.
The most commonly spotted animals were seals, which were often around Canary Wharf in London. Many of these sightings were reported by people who saw the aquatic mammals from skyscrapers around the city.
City residents also reported sightings of 444 dolphins and porpoises and around 49 whales.
Joanna Barker, manager of European conservation projects for the Zoological Society of London, said that many people only see a dirty and environment when they look into the River Thames.
Barker explained that beneath its waves, the river is actually full of life. She said that the Thames has a wide range of invertebrates and fish, as well as animal predators.
The amount of pollution in the Thames reached significant levels that the river was declared to be "biologically extinct" 50 years ago. It was considered to be too dirty for any living creature to survive in it.
Recent sightings of marine mammals, however, confirm that the Thames is recovering its former vitality. This suggests that animals are once again venturing further into London's waterway.
According to reports, seals were spotted as far upstream of the river as Teddington, as well as the Hampton Court Palace located in the city's south west area.
Porpoises and dolphins were seen at Teddington Lock, with pods sighted near Deptford and Kew Gardens.
In 2006, bottle-nose whale was spotted in central London, but the animal did not survive its journey. Other whales were also sighted near Gravesend in Kent.
Barker said that the high number of animal sightings in London suggests that the stocks of fish are also moving in to the area to support these marine mammals.
Aside from recent reports from the public, the ZSL's animal conservation team has also begun conducting detailed surveys of seals along the greater estuary of the Thames.
The team has made use of boats and planes to count the number of individual seals along the River Thames for the past three years.
Photo: Ronald Saunders | Flickr