The short answer

Yes — you can swim in the River Thames, but the tidal stretch through London is a working river. Strong tides, commercial traffic and changing water quality mean the realistic, safe way to swim it is as part of an organised, permission-led event.

Is it legal to swim in the Thames?

On the tidal Thames the Port of London Authority (PLA) is the navigation authority. Swimming between Putney Bridge and Crossness is restricted and generally requires prior written permission from the PLA. Organised events apply for that permission in advance and operate inside an agreed plan.

Upstream of Putney and on non-tidal stretches there are more recognised places to swim, but local rules, lock keepers and riverside landowners still apply. If in doubt, don’t jump in.

Why the tidal Thames is different

• Tides move at up to several knots — far faster than most swimmers.
• Large commercial and passenger vessels share the river.
• Water quality varies with rainfall and storm overflows.
• Entry and exit points are limited and often slippery.

The organised, safer way

Swim London is built around the river, not imposed on it. The event runs with PLA engagement, a professional swim safety lead, tide-assisted timing, tow floats and clear go / no-go criteria tied to weather and water quality. That’s what makes a serious Thames swim possible for capable open-water swimmers.

Read more about how we approach this on the safety approach page, or see the 10 km and 5 km distances.

Quick FAQs

Can I just go for a Thames swim in London?

Not in central London. The tidal river through the city centre is restricted and dangerous outside of organised events.

What about cold water and water quality?

Both are real factors. Organised events monitor water quality against published thresholds and plan around them. Cold-water acclimatisation and prior open-water experience are essential.

How do I take part in Swim London?

Join the priority entry list — you’ll hear first when entries open, with full briefing and standards details.