Castle to Castle Challenge – the ultimate 20km Menai Strait Swim

Take on the Castle to Castle Swim Challenge – a 20km open-water adventure between Beaumaris Castle and Caernarfon Castle down the legendary Menai Strait. Swim through fast moving tides, breathtaking scenery, past historic bridges and wildlife, fully supported by our safety team and expert guides. This unique endurance event offers challenge, camaraderie, and an unforgettable journey along one of Wales’ most iconic waterways. Limited entries — register now to swim between the castles and conquer the Strait!

The Menai Strait

The Menai Strait (locally Afon Menai) is a 16-mile sea channel separating Anglesey from mainland Wales. The only way across other than by water is by Thomas Telford’s Menai Suspension Bridge—a Grade I listed structure nearly two centuries old, and Robert Stephenson’s Britannia Bridge, which carries both road and rail. Varying in width from 400m to three-quarters of a mile, the Strait takes its name from the Welsh main-aw, meaning “narrow water.” Its central stretch, the Swellies, is renowned for powerful reversing tides, whirlpools, and submerged rocks, making expert navigation essential! Designated as part of the Menai Strait and Conwy Special Area of Conservation, it hosts diverse habitats—mudflats, salt marshes, limestone reefs—and abundant wildlife, from crabs, sponges, and fish to wading birds like oystercatchers and curlews, and even seals and harbour porpoises playing in the tidal races.

The Castles

Beaumaris Castle and Caernarfon Castle are two iconic strongholds built by King Edward I in the late 13th century as part of his conquest of Wales. Beaumaris, on the Isle of Anglesey, overlooks the Menai Strait and, though never completed, remains one of the most beautifully designed castles of its time. At the other end of the Strait on the main land, Caernarfon Castle rises above the River Seiont, built as both a royal residence and a symbol of English rule. Today, both are part of a UNESCO World Heritage Site and stand as powerful reminders of North Wales’ turbulent medieval past.

The Castle to Castle Swim

Total distance: 20km (tide assisted)
Price: £170pp (+£5 booking fee per person)
Meeting location: Caernarfon
Places available: 12 people max
After booking you may be asked for evidence of your ability – see below.

It’s not a race!

This is a guided swimming challenge, not a race. It is imperative for safety that we all stay together and move at the same pace. You will not be allowed to swim off ahead and no one will be left behind! With this in mind please do consider the duration of time you will be in the water

We will provide the following:

The ratio of safety crew to swimmers will be 5:12

• A unique ‘I Swam The Menai Strait!’ swim cap!
• Fully licensed and insured event: You can rest assured you will be completly safe in our hands.
• Qualified guides: You’ll have no worries about getting lost, just relax and enjoy your surroundings and the swim!
• Water safety & support: We will have a power boat driven by crew experienced in negotiating the waters of the Strait. We will also have an experienced safety kayaker who will guide you through the tricky sections and a tail end kayak guide to keep an eye on everyone and make sure we all stay together. An open water lifeguard qualified swimming guide will also be present to offer support. If you get too tired or too cold to finish the swim you will be able to get into the safety boat to finish the journey.
• First Aid: There is a First Aider stationed in the safety boat. All guides are first aid trained and will be carrying first aid kits.
• Transport to the start: We will taxi you to the start of the swim and we will swim back to the location of your cars.
• Free photographs of your adventure taken from the boat.

Pace, Ability & Experience

You MUST have previous experience of endurance sea swimming in choppy conditions and be a confident and strong FRONT CRAWL swimmer. This swim is a committing and dangerous undertaking. Please be sure that your swimming ability is in-line with the criteria set out below and that you are happy with the our terms and conditions before entering. If during the swim you are unable to keep up with the group you will be retired from the swim.

The swimming speed of the members of the group will vary so please be aware that you may not be traveling as fast as you might if you were swimming alone! The emphasis is on keeping going, not speed! The pace will be dictated by the guides, taking into account the ability of the group as a whole. You will need a high level of fitness to take part and will need to keep moving at a good pace to keep warm. If you struggle during the event and this begins to impact on the well being of the rest of the group we will politely ask you to get into the support boat.

All participants must be 18+ years old.

To take part in the 20km swim you should:
– Be able to swim front crawl at a minimum speed of 1km per 21 minutes with no rests (in calm, still water or a pool)
– Be able to swim 5km in one go with minimal rest.
– Be able to put in bursts of a few minutes strong, fast, front crawl swimming when required to during this distance.
– Have plenty of experience of swimming in rough sea conditions and fast flowing water and be very happy and confident in this environment.
– Be able to provide evidence of your swimming ability and other recent endurance swims undertaken of at least 10km in distance.

Being used to sea swimming in rough conditions is very important – you must be comfortable with the salt water, low water visibility, waves and strong currents. The tides in the straits are very strong and fast so you need to be a confident and strong swimmer. At times you will be required to swim fast, navigate across the channel of water, sometimes fighting waves and strong currents. This requires speed and strength. There is limited opportunity to stop and rest in the swim but there will be times when we can float along with the current. Although it is a 20km swim, the fast current will carry us a long way so it will actually feel more like half the distance (Approx 4 hours in the water).

Non-wetsuit swimmers

We are now allowing non-wetsuit swimmers to take part in the Menai Strait swim – you must have the same experience listed above for the distance you want to complete AND this experience must have been completed when you were not wearing a wetsuit. You must also have swum non-stop for a minimum of 3 hours in cold, choppy water. Please consider your ability carefully before taking part in this swim without a wetsuit. We reserve the right to retire you from the swim at anytime should we deem you unfit to continue.

Equipment required:

Tow float are compulsory – NO EXCEPTIONS!

Compulsory kit:
– Brightly coloured swimming specific tow float
– Yellow coloured swimming hat that Love SwimRun will supply

We highly recommend that you wear a wetsuit to give you extra buoyancy and to protect you from the cold and from jellyfish stings. If you do not wear wetsuit it is at your own risk. See above for necessary experience.

We recommend you wear/carry:
– Wetsuit: Full or shortie (we highly recommend full as we could be in the water for a while and there may be jellyfish)
– Thermal/insulating layers underneath: rash vests or neoprene vests
– Neoprene accessories – gloves, socks, hat
– Googles
– Energy gel or bar and bottle of drink (can be carried on boat but you are better off carrying in a doughnut style tow float for access as you require it)

How to enter

Before you enter, please be sure that you have the necessary swimming ability and experience (listed above) to complete the swim safely and to enjoy it! Please use the buttons next to the dates available above and fill in the entry form as directed. Please read the terms and conditions fully before agreeing to them.

Entries will be at the discretion of Love SwimRun Ltd. You may be asked to provide evidence of your swimming ability and experience. Acceptability of experience is the decision of Love SwimRun Ltd. The decision of Love SwimRun Ltd. is final and no disputes will be entered into.

Further Information

Further information on kit and logistics on the day will be available a few weeks before the event.