Join the Mariners Mile Swim on September 27, 2025, for a scenic and supportive open water challenge in Hertfordshire’s Lea Valley. Perfect for swimmers of all levels, this event combines nature, sport, and community in a memorable way.
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Difficulty
easy
Duration
1–2 hours
Fitness Level
Swimmers should have a basic level of cardiovascular fitness and comfort in open water.
Wildlife
History
Lea Valley has been a vital waterway for centuries, historically supporting trade and recreation, now serving as a popular open water swimming spot.
Conservation
HYMB emphasizes sustainable practices, such as river clean-up initiatives and eco-friendly event management, to protect this natural resource.
Herts Young Mariners Base
Join the Mariners Mile Swim on September 27, 2025, for a scenic and supportive open water challenge in Hertfordshire’s Lea Valley. Perfect for swimmers of all levels, this event combines nature, sport, and community in a memorable way.
Herts Young Mariners Base is an outdoor water activity centre located in Cheshunt, Hertfordshire, in the Lea Valley. The base runs a range of supervised lake-based activities for young people and adults, including sailing, canoeing, kayaking, stand-up paddleboarding (SUP), raft building, fencing, archery and climbing. Herts Young Mariners Base offers structured courses and one-off sessions: RYA Stage 1 three-day beginner sailing courses for children; BSUPA Level 1 “Ready to Ride” two-hour SUP introductions; coached canoe and kayak sessions for adults; and regular adult paddle sessions for experienced participants.
The venue hosts organised events such as the Mariners Mile Open Water Swim and monthly “Adults Come and Try Activities” evenings. The Mariners Mile is an open water swim event held at HYMB in Cheshunt, with distances for different abilities and a minimum age of 14 for participants; a portion of the event fees supports Cancer Research UK. Adult swim sessions and coached paddles run on set evenings and weekends, with changing rooms and refreshments available on site.
Herts Young Mariners Base uses qualified instructors for coached sessions and accredited courses, and schedules beginner-focused and skill-development opportunities for different ages and abilities. The base operates a mix of instructor-led courses and non-instructor-led sessions, providing options for certification, coached progression, or relaxed recreational use. Its location in the Lea Valley provides accessible open water and flat-water environments suitable for learning, training, and organised events.
Booking info, session times and entry requirements are on the base's event pages; check before attending for exact details.
Location
Cheshunt, England
Lea Valley in Hertfordshire
Scheduled Sessions
Monthly & Weekly
Regular adult and youth sessions
Ages Accepted
14+ (events & swims)
Teens and adults welcome
Events & Courses
Multiple experiences
Sailing, paddling, SUP and swims
Reserve a spot for a course, coached session or the Mariners Mile — secure online booking and clear event details make it easy to join.
Wear appropriate swim gear
Ensure your wetsuit or swimwear is suitable for cool water temperatures and comfortable for a prolonged swim.
Hydrate beforehand
Drink plenty of water before the race to stay hydrated during the swim.
Arrive early
Give yourself plenty of time for warm-up, registration, and acclimating to the water.
Check water conditions
Be aware of weather and water temperature on race day to adjust gear accordingly.
Wetsuit
A wetsuit helps maintain body temperature and provides buoyancy in open water.
fall
Swim cap
A swim cap reduces water resistance and keeps hair out of your face.
Goggles
Goggles protect your eyes and improve visibility underwater.
Towel
A towel is handy for drying off and warming up post-swim.