IJsselmeer Zwemmarathon

The IJsselmeer is a vast, man-made freshwater expanse that demands a specific kind of respect from those who swim its length. Formed in 1932 by the completion of the Afsluitdijk, this basin replaced the saltier Zuiderzee, leaving behind a shallow, predictable floor with an average depth of just 4.5 meters. To swim here is to move across a landscape that was once a bustling commercial sea; as you pull through the water, you are essentially traversing the top of a lost medieval geography. The water carries a distinct, flat quality, shaped by the engineered boundaries that define its character today.

Historical currents and landmarks

As you navigate the 22-kilometer marathon, your line takes you past the enduring legacy of the Dutch maritime golden age. You will pass the historic Peperhuis, a 17th-century VOC warehouse that once overflowed with exotic spices and goods from Asia, now standing as a silent witness to the city's former herring fleet, which collapsed after the damming of the sea. Further along, the masonry of the Zeemuur seawall—dating back to 1608—still guards the eastern edge of Enkhuizen, its Staverse Poortje gate once the singular point of entry for the town. The history here is layered; in 1421, a catastrophic storm flood erased the original 'Oostdorp' settlement, forcing the construction of the current city landmarks using salvaged materials from the drowned church ruins. Modern engineering also leaves its mark, as swimmers occasionally pass near the Naviduct Krabbersgat, the world’s first naviduct, where ships transition between lake levels in a seamless mechanical ballet.

Race day logistics

The IJsselmeer Zwemmarathon remains one of the most demanding tests in the region, requiring each athlete to be accompanied by a dedicated support boat for the entire 22km crossing. This logistical necessity ensures safety across the open water, where conditions can shift rapidly despite the shallow depth. The event starts at 10:00 AM in Stavoren, drawing those looking for a longer challenge than the shorter, related swims like the 10km Race Medemblik. Whether you are aiming for the full marathon distance or observing the finish in Medemblik, the experience is defined by the sheer scale of the freshwater reservoir under the expansive Dutch sky.