5150 KNOKKE-HEIST in the stunning region of Flanders, Belgium. Swim - Conquer the North Sea: The adventure begins with a heart-pounding 1.5km (0.93 mile) swim course right in the North Sea, just in front of the bike park at Heist beach. Imagine the rush as you dive into the crystal-clear waters, surrounded by the salty breeze and the thrill of the open sea. The course promises a challenging yet invigorating start and finish approximately 800 meters apart, giving you a taste of the ocean's ...