This post is in the front page of HN because of this initial confusion. Otherwise that was no larger deal compared to other projects that are going on around the world.
And there's plenty of cool about this project, from the reusable kingsize lego-like blocks used to strengthen the dike, to the meandering river for fish passing throuh the dike. There's also a VR video.
They need to get out to sea to make a journey to make offspring. That offspring sometimes gets caught in France on the way back, where it is grown and sold in the Netherlands. Fishing results from IJsselmeer can also be found in shops but they are not easy to catch anymore. I would think, for statistic reasons, the caught eels in France might be more sustainable than catching grown eels in the IJsselmeer. The real solution is to work out better sluices and pump stations, so fish can pass again.