12 interesting facts about the Thames River in London

The River Thames is the longest river entirely within England, stretching about 215 miles (346 km) from its source in the Cotswolds to the North Sea via the Thames Estuary. While the central section is a focal point, the river actually flows through several counties and has 45 locks on its non-tidal section.

From your Thames River cruise, you'll pass the historic Tower of London. A fun fact about this landmark is that in 1251, King Henry III kept a polar bear, a gift from the King of Norway, at the Tower's zoo. On hot days, the bear was reportedly allowed to swim and fish in the River Thames.

Historically, the River Thames used to freeze over completely during the winter, allowing people to hold "Frost Fairs" on the ice between the early 1600s and 1814. These fairs were huge events with food, drinks, sports, and stalls. The river is much cleaner and rarely freezes now, but the history is a great fact.

While London Bridge and Tower Bridge are the most famous sights on a Thames River cruise, the entire river is crossed by over 200 bridges, from small footbridges to grand Victorian structures. This count includes road, rail, and pedestrian bridges, each playing a vital role in connecting the city and its history.

Upstream of London, the River Thames has an alternative name as it flows through Oxford: the River Isis. This literary name is still commonly used in that area. This dual naming is a fun piece of trivia to share with your group while on a Thames River cruise.

A surprising Thames River cruise fact is that around two-thirds of London's drinking water is sourced directly from the River Thames. The water undergoes extensive and modern treatment before it reaches homes, showing how crucial the river remains to the city's daily life, far beyond tourism.

The river was once declared "biologically dead" in the 1950s due to severe pollution. Thanks to decades of conservation work and sewage system improvements, a Thames River cruise can now boast a sighting of over 125 species of fish, as well as seals and even rare marine mammals like porpoises.

As you pass the pedestrian-only Millennium Bridge on your Thames River cruise, remember its famous nickname: the "Wobbly Bridge." When it first opened in 2000, it swayed unexpectedly, forcing it to close for nearly two years for modifications. It has since reopened, safe and solid.

The Thames Path is a designated National Trail that follows the river for approximately 184 miles (296 km), making it the longest riverside walk in Europe. Your Thames River cruise allows you to see portions of this path, which is popular for walking and cycling.

The River Thames is tidal all the way up to Teddington Lock in south-west London, meaning the tide from the North Sea flows in and out, creating powerful currents. This tidal nature is why all Thames River cruise operators carefully plan their sailing times, especially for longer journeys.

The River Thames is home to the world's oldest boat race, "Doggett's Coat and Badge," which began in 1715 and is contested by watermen and lightermen. This historic race was only postponed for the second time in over 300 years in 2020 due to the pandemic, highlighting its incredible longevity.

The Thames Barrier, completed in 1982, is a truly modern Thames River cruise fact. It is London's primary defence against catastrophic flooding from North Sea tidal surges and is the world's second-largest movable flood barrier, surpassed only by the Oosterscheldekering in the Netherlands.