Key Facts


The 4k Lock to Lock swim from Eynsham Lock to Kings Lock follows the River Thames downstream through the picturesque landscape of Wytham Woods and Oxford University pastures. Swimmers should be familiar with open water swimming and be able to complete the 4k distance. Wetsuits are mandatory unless you gain our permission in writing before the event. If in doubt please contact us regarding your previous open water swimming experience.


Frequently asked questions:

Does the river have a fast flow?

We swim this stretch of the river regularly. The flow differs from one day to the next based on factors such as rain fall, opening of locks etc. The flow is generally fairly slow but we have noticed a difference of 15 minutes on our total swim time dependent upon flow rate. Up to date information can be found at

How long will 4k take me?

Everyone swims at a different pace but the fastest recorded time for this event is 42 minutes. Our more leisurely swimmers enjoy the swim for up to 2 hours 45 minutes.

Which side of the river should I swim on?

The Environment Agency, who grant us permission to run the Lock to Lock event, ask that swimmers stay to the right of the river wherever possible. Boats and other river users also navigate on the right so, as river users, we need to adhere to the same rules. There are occasions when it is safer to swim closer to the middle of the river: There is one tight corner approximately 3k along the route where the water gets very shallow on the inside bend making it possible to touch the river bed. On some of the tree-lined sections of the course there can be obstacles such as submerged branches and tree roots that could be dangerous or cause injury if snagged. Our safety kayakers will help alert you to these obstacles en-route.

Do I have to wear a wetsuit?

Wetsuits are mandatory for this event unless you are an experienced open water swimmer and have our permission, in writing, in advance to swim without. Please contact us at for permission.

Will the swim be a timed event?

Yes, the event is timed.

When will results be available?

We aim to have results available online within 48 hours of the event finishing.

Will I be safe in the water?

Safety is our utmost concern. We have safety kayakers paddling with you along the length of the course and we have spotters on the shore. We also have medics at the event should you require any medical attention.

What if I feel I can’t finish the swim?

We hope that everyone will have trained enough to complete the full length of the course. However we do realise that this may be the first time some participants have swum this distance in a river and we will have support boats nearby should you experience any difficulties. There will also be exit points along the course.

Is the water clean?

The water will be tested to environmental safety standards before the swim. Since 2015 all water tests have passed with a “high” cleanliness rating.

What will the water temperature be?

The water temperature will very much depend on weather conditions leading up to the event. In September 2019 the water temperature was between 15-18 degrees centigrade.

Is there a chance of becoming ill during the swim?

Public Health England publish a leaflet on the risk of illness when open water swimming, which can be viewed here: We always follow these guidelines and have never become unwell during or after swimming this stretch of the Thames. Public Health England recommend...Before you swim to cover cuts, scratches or sores with a waterproof plaster before swimming, consider wearing appropriate protective clothing such as a wetsuit, gloves and/or protective footwear. While you are swimming try to avoid swallowing and/or splashing water into your mouth, observe local safety advice. After swimming ensure you clean your hands thoroughly with soap and water after swimming and before handling/eating food, thoroughly clean cuts or abrasions using soap and water, handle your wetsuit with care after use, rinse it with clean water as soon as is practicable after swimming, clean with detergent and rinse as advised by the manufacturer, always wash your hands with soap and water after handling or cleaning your wetsuit and allow the suit to dry thoroughly before reuse.

Where can I park?

Siemens Magnet Technology, very close to the start of the swim, allows us some parking spaces. There is also space for additional cars on the road leading up to Siemens. We request, where possible, that you car-share to limit the number of parking spaces being used. We cover the cost of the car park so parking is free for our competitors. There is additional, overflow parking nearby.

So I park at the start of the swim course. How do I get back to my car?

There are 3 options...
a) We recommend that you take the shuttle bus from the end of the swim back to Seimens car park. Please pay for the shuttle when you register. You can buy more than one bus ticket if a friend would like to walk the towpath to watch you and travel back with you.
b) You can leave a car somewhere in Wolvercote then car share to the start (Eynsham Lock). Be aware there is very limited parking at the start and a toll to pay on one of the bridges.
c) When you finish the swim you can walk back to the start, however it is a 4km walk along muddy tow paths and can take well over an hour.

I’m often nervous before this type of event. What if I need the loo?

We get nervous too! There will be toilets at the start and end of the swim.

What should I do with the clothes I want to change into after the event?

Registration will take place in the field next to Eynsham Lock. There will be a changing tent next to registration. Put a towel any clothes you would like for the end of the swim in a bag and hand over to our marshals. Your bag will be transported to the end of the swim ready for you to change into. There is a changing tent at the end of the swim too.

What do I do with my car keys?

We advise you to put your car keys into your clothes bag. We have a system in place to ensure that you are the only person who can retrieve your bag at the end. Please note that we cannot accept responsibility for any loss or damage to personal items left in your car.

What do I do while I’m waiting for the bus at the end of the swim?

When you’ve finished your swim and changed into your warm clothes we invite you to enjoy a fresh coffee or tea in your souveneer mug with a slice of homemade cake – included in your ticket price. Dependent upon the number of competitors at the event you should have to wait no longer than approximately 15 – 30 minutes to get a bus back to your car.

Can under 18s swim in this event?

For this particular event we are able to get insurance for 14s and above however, in addition to signing the waiver when you buy your under 18s ticket, you must send a letter from a parent/guardian stating that your child is a strong swimmer, swims regularly with a club and has previous necessary open water experience, swimming against adults. This must be signed and emailed to This must be received by us no later than one week prior to the swim event date.

I can swim in the Thames any time for free so why do you charge?

Yes you can swim in the Thames any time, and we do, which is how we discovered this lovely stretch of the river. You can also run 26 miles through the streets of London free of charge, any day, but still thousands of people choose to enter the London Marathon each year. Our event enables you to swim in an organised swimming event and to enjoy the experience with other like-minded people. Our ticket price covers a multitude of items including… car parking, water testing, event insurance, rescue kayaks, rescue boat, paramedics, swim caps, souvenier mugs/medals, tea/coffee/cake, timing chips, WC hire, registration and changing tents, river licenses etc. It also covers the time it takes us to actually organise the event and liaise with local land owners and the Environment Agency, and our annual costs of publicising the event and maintaining our website.

What if I have more questions?

Please email us at and we will endeavour to answer your questions as quickly as possible.