Date: Sunday 10th August 2025
Location: Marlow
Charity Entry: £20 (usually over £100)
Fundraising Target: £250

Half Marathon: approx. 5.5km
Mid-Distance: approx. 9km
Full Marathon: approx: 13km
3 Person Relay: approx. 13km

The Thames Marathon is an endurance swim between Henley-on-Thames and Marlow with a choice of 3 distances. It covers a beautiful stretch of the Thames and has become one of open water swimming’s most prestigious marathon swims.

The Event Village will be in Marlow, swimmers will be transported by coach to the full, mid or half distance start, and will swim back to Marlow. There is also the option to walk or run to the start of the half-marathon.

Distances

  • Half Marthon

    Approx. 5.5km

    The swim is split into 3 sections. Swimmers will be required to exit the water at the 2 locks (Hurley and Temple) where drinks and energy snacks will be available.

  • Mid-Distance

    Approx. 9km

    The swim is split into 3 sections. Swimmers will be required to exit the water at the 2 locks (Hurley and Temple) where drinks and energy snacks will be available.

  • Marathon

    Approx. 13km

    The swim is split into 4 sections. Swimmers will be required to exit the water at the 3 locks (Hambleden, Hurley and Temple ) where drinks and energy snacks will be available.

  • 3 Person Relay

    Approx. 13km

    Each person will swim one 4/5km section of the course and walk two. All team members will be taken to the start of the course with handovers at Hambleden and Hurley Locks.

A Note About the Distance


The actual distance that you swim will depend upon several factors including the start and finish points, the precise course (inside or outside of the bends), how straight you swim (zig zagging even slightly can make a difference across this distance) and the exact location of the exits and re-entries around the locks and weirs. Some of these variables will not be confirmed until much closer to the event.


On average the distance travelled will be around 5.5km, 9km or 13km however this is not ratified.

Level Water: The Power of Swimming

Level Water provide 1-to-1 swimming lesson for children with disabilities across the UK. Life changing lessons that teach them the essential skills to learn to swim and fall in love with the water.

Henley ThamesMarathon - FAQs

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