"Harder than Ironman, Fairer than Ironman."

Andrew Fisher, First Isoman Champion. Click to read review

"Martyn Brunt of 220 takes on the Isoman..."

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The Zone3 Marathon Swim

7 Miles (11.2 km)

The Zone3 Half Marathon Swim

3.5 Miles (5.6 km)

The Zone3 Quarter Marathon Swim

1.75 Miles (2.8 km)

2017 Entries Now Open: Enter Here


The Isoman Zone3 Swim

Zone 3

1st July 2017 - Arrow Valley Park, UK (B98 0LJ)

Isoman Zone3 Big Swim

Take on the "real" swimmers marathon.

The 10km swim is often regarded as the swimmers' marathon, but with a world record time of just under 1 hour and 52 minutes set by Oussama Mellouli, it falls short of the world record for the running equivalent (currently just under 2 hours and 3 minutes). Consequently, at Isoman, we decided to even it up. So, using the world records and a formula that predicts tiredness, we have calculated how far the fastest 10 km swimmer would get in 2 hours and 3 minutes. The answer is 7 miles! The true swimmers marathon? (Read More...)

Medal, Goody bag, T-Shirt and Party! And the chance to be part of this spectacular day of endurance!

Sign up here for the 7 mile Full Marathon Swim

All abilities welcome?

Not quite ready for the full marathon yet? No problem - we have something for everyone with the half and quarter distances.

One of our guiding principles with setting up Isoman was to make it inclusive, not only to elites, but to beginners alike and create a single day of endurance where individuals from the swimming, cycling, running and triathlon community can all come together and enjoy the sports we love.

Sign up here for the 3.5 mile Half Marathon Swim

Sign up here for the 1.75 mile Quarter Marathon Swim

Fancy a face off with your running or cycling buddies?

As we believe we have equalised the three disciplines of swimming, running and cycling (yes, we've created a similar event for cyclists too!) in terms of the level of excellence required to acheive a similar time, this gives you the opportinity to challenge your running or cycling buddies to a race to see who's the best athlete, All events will take place on the same day - nowhere else will you get the chance for such a face off.

Most equal of Triathlon Relays?

Or better still get together with 2 of your friends and do the relay. Nowhere else will you find a race where the legs are more equal!

Sign up here for the Relay.


The course involves 2, 4 or 8 laps of the Arrow Valley Lake with a nutrition jetty accessible on every lap.

Chip timing will also be available with an in water timing gate providing valuable split time intervals!

Party In the Park

Make sure you pack your dancing shoes. We'll have music all day with live music at the main stage in the expo field from 2pm onwards to welcome the athletes competing in the Isoman home.
Come and enjoy a beer or two and party the afternoon away! It is saturday afterall so no work in the morning!
There will be bouncy castles and other activities for the kids to take part in, so bring them along too! Whether you're taking part, watching loved ones or simply want to come and see what it's all about, you're all welcome.

Line Up

Completely Covered

The Mighty BACCHUS

Stuart Woolfenden

Music Like Lemons

dB Smith - Bluesman

Bloodwise - Our official Charity Partner

The party is being held in aid of Blood Cancers, and everyone is welcome. So come along, enjoy the show, drop a bit of your loose change in the buckets provided/buy raffle tickets and feel good that you're helping such a great charity. Isoman profits from the expo field will all be going to the charity. And if you're taking part in one of the challenges, then don't forget you can also raise money that way too. When registering, please leave the "Agree To Our Charity Partner Contacting you" checked and Bloodwise, formerly Leukaemia and Lymphoma Research will send you through a sponsorship pack.