There doesnt seem to be anything...
Its often thought that the waterways in London dont support much life, but surveys regularly show that the rivers and canals of the capital are teeming with wildlife. The Thames has seen a whale, although that affair ended sadly. Seals are quite common on the Thames and have been spotted as far upstream as Hampton Court. Otters are making a comeback (Newsswire and BW newsletter) and terapins seem to be declining. A novelty is the recent announcement that seahorses are breeding in the Thames (see BBC News) Birds are also a strong feature, the obligatory heron being one, but a recent newcomer is the cormorant, at one time this was a rare sight, and one remembers how almost every one of those navigation channel markers across Breydon Water seemed to have a Cormorant sitting on the top! The bird is now seen on most of London's waterways, and it seems just as comfortable at Camden Locks not that far away from the tidal Thames.
Diversity abounds on the London waterways despite perceptions that they are dirty and polluted. Otters are now found, and if reports froma couple of years were to be belived, the aliigators could also be found in the River Lea! Seriously from a reptilian viewpoint, large terrapins can occasionally be seen on the Regents Canal, and I expect it wont be long before we get crocodiles snaping at the heels of people as they walk along the popular London towpath routes!
One major stronghold for wildlife happens to be the short stretch of Regents Canal where it runs through the zoological gardens. There is a good variety of birds in the Snowdon Aviary on the north side perimeter, and animals such as Hyneas at the main site. Whilst boating through the zoo, do not forget to studiously observe those human species as they make their way around the zoo - its a case of who's watching the watchers. Scientists who were observing monkeys found themselves being observed in turn by the monekys. In the same way as artists say that viewers become part of the artwork, the visitors to the zoo become part of the zoo itself. Studious observations on human lifeforms do not have to be concentrated at the zoological gardens or anywhere along the Little Venice - Camden towpath for that matter a much better place would be the markets and high street at Camden where all manner of human life-forms can be observed, ranging from the sensible laid back species to the more downrightly outrageous examples! What do the animals think of us? It seems they're not very impressed with our species!

The classical view - swans with cygnets seen at Cumberland Turn in
Regents Park May 2006

Really big fish! Seen in the River Lea (Lee Navigation section)
just above Ware lock on a hot summer's day in July 2006

Shiver me timbers its a heron! Spotted whilst Pirate Princess was
passing through Little Venice in August 2006

Cormorant at the head of Hampstead Road locks in March
2008

Coot with compulsive plastication disorder (collecting the detirus
of human garbage!) seen on the Hackney Canal section of the Lee
Navigation in June 2006

June 2006 - Heron on the Hackney canal watching over those strange
inavders - plastic bottles!