Hever Castle 10K Marathon Swim

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Simon Griffiths enjoyed a long swim at one of Britain’s most famous stately homes

The beauty of outdoor swimming is that every swim is different and each throws up its own challenges and rewards. Whether or not you embrace and overcome those challenges determines your enjoyment of the swim. The challenges at Hever Castle included swimming through duckweed and lilies, varying water temperatures and occasional patches of shallow silty water. To me, that made the swim more adventurous, although I can see it wouldn’t be to everyone’s taste. But if you wanted clear water and straight lines, you’d stick to pool swimming, wouldn’t you?

A welcome touch of wildness

Castle Triathlon run a series of triathlon events with links to castles in England, Ireland and France. Recently, they have added swim-only options at these events. For the first time in 2018 they included a 10km marathon swim at their Festival of Endurance at Hever Castle in Kent, which took place in early July.

At this point we should mention that Outdoor Swimmer is a media partner with Castle Triathlon and we have offered suggestions and advice around the creation of events for swimmers. We also receive a commission for entries to events using our discount code.

That said, we only agreed to work with Castle Triathlon because Hever Castle is a unique place to swim. The backdrop, naturally for one of Britain’s most famous stately homes, is amazing. The swim takes place in a man-made lake (dug out by hand more than 100 years ago) and a small stretch of the River Eden, creating a circular course of roughly 2km around an island. The lake is calm and warm, with plenty of space, while the river section is notably cooler and narrow in parts. It’s the river section that gives this swim a welcome touch of wildness.

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With the water temperature over 24 degrees, this was a non-wetsuit swim

A friendly group

The 10km swim kicked off early – at 6:15 in the morning to be precise. This meant the sun was low over the lake and it looked stunning, but it made sighting difficult in places. With the water temperature in excess of 24 degrees, the organiser made this a non-wetsuit swim. There were only 17 of us for the 10km swim (the 1.9 and 3.8km options attracted more), which made for a friendly group. The swim starts just in front of Hever’s Italian loggia, which we also passed on each lap. The organiser provided energy drinks, jelly babies and gels, and also left space for us to leave our own nutrition on the loggia steps. This therefore gave an opportunity to refuel every 2km, which was perfect.

Th e lake is shallow and silty, so visibility is low in the water. Apart from the sun, sighting was easy and navigation straightforward with large buoys every 100m. After a three-quarter loop of the lake you enter the river channel. The best line is to the left to avoid a particularly shallow section and a large patch of lilies. As you pass under a footbridge (a good place for supporters to watch), the channel narrows and can get a little congested with swimmers. Navigation in this section is easy as there is only one way to go. Here, unless overtaking, stick to the middle to avoid overhanging trees and the occasional underwater stump near the edge. You need to sight often because of twists and turns in the channel. As you approach the end of the channel there is a noticeable drop in water temperature and there are a couple of wide patches of duckweed. While the duckweed looks a bit off-putting from above, once you’ve swum through it a few times you find it doesn’t impede your swimming. There is then a sharp bend to the left and another footbridge to pass under before you re-enter the lake and either start another lap or head to the finish.

September swim

This isn’t a swim for setting personal records but it’s definitely an enjoyable way to pass a few hours swimming. Castle Triathlon run two events a year at Hever, with the 10km part of their July event. There is a 5km option in September.

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Fuelling at the Italian loggia


Name: Hever Castle Swim

Water type: man-made lake plus river

Distances: 10km (plus 3.8km and 1.9km options)

Wetsuit policy: British Triathlon guidelines applied.

Water temperature: 24.5 degrees in2018. Usually between 18 and 22 degrees.

Further information: www.castletriathlonseries.co.uk/castle-swim-series/

Cover Web Image

Issue 42 October 2020

  • Q&A with Jaimie Monahan - marathon swimmer and Queen of the Ice
  • Autumn swim adventures around the UK
  • The science behind cold water acclimatisation
  • Reviewed: The Best Open Water Goggles
  • The often deadly history of unsupported marathon swims

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