The Thermal Helix is lined with a mid-weight zirconium jersey, chosen because it dries quickly, minimises weight and is flexible.

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The suit was tried by professional triathlete Sara McLarty at last year’s Escape From Alcatraz Triathlon where the swim is held in the chilly waters of San Francisco Bay.

 Sara said: “The Thermal Helix made a huge difference in the temperature of my core and extremities while swimming in water below 55 degrees [12 degrees Celsius]. Just like the other Helix models, it maintained it’s flexibility, comfortable fit, and buoyancy in all the right places.”