River Thames now fit for porpoise, says wildlife study

She said that the Thames has a wide range of invertebrates and fish, as well as animal predators.

The sightings, often by members of the public, were recorded between 2004 and 2014 as part of the ZSL Thames Marine Mammal Sightings Survey, an extension of which is still ongoing.

The sealife have been seen swimming in the Thames Estuary along with other underwater friends, including porpoises and dolphins.

But now the River Thames has become a hotspot for sighting some of out best-loved marine mammals, according to a 10-year survey by the Zoological Society of London (ZSL).

Harbor seals were the most commonly sighted marine mammal, with 1,080 animals reported. Seals were also spotted as far upstream as Teddington and Hampton Court Palace in southwest London, while dolphins and porpoises were spotted at Teddington Lock, as well as near Kew Gardens and Deptford.

It was only 50 years ago that the Thames was so polluted that it was deemed to be too dirty for any biological life to survive there, according to BBC News.

A northern bottlenose whale famously swam up the Thames past the Houses of Parliament in 2006 but failed to survive.

“As a top predator, their presence is a good sign that the Thames is getting cleaner and supporting many fish species”.

Scientists at ZSL have used planes and boats to count the number of seals on the Thames annually for the last three years, estimating that there are around 670 harbour seals along the estuary.

“We do think this area is really important”, said Miss Barker.

The survey revealed the highest amount of marine animal sightings in the last ten years.

ZSL has asked the public to send in their photos of marine mammals, in an effort to help further research into life beneath the waves.