A trail of white water runs through the middle of the dark water of the forum pond. It has been made by first-year student of Meteorology Joeri Messelink, who is training in the pond for a half triathlon.
Why do you choose to swim in the pond rather than the swimming pool?
'I enjoy swimming out of doors. We usually always train out of doors in the summer but I didn't have much time this summer. Like this I can still do some swimming out of doors. I am planning to do the Ironman 70.3 next summer. For that I will have to swim 1.9 km, cycle 90 km and run a half marathon. From the bridge to the end is about 200 metres and after the first length it isn't cold anymore.'
Is the water really clean enough to swim in?
'People say the water quality is poor but it is fine for swimming in. I have already swum here seven or eight times and have never been ill yet. The water is clean enough and I think it is nonsense to forbid swimming here, so in fact I also want to make a statement. It is perfectly good water for swimming in.'
Where does your love of swimming in natural water come from?
'I started last year in Montenegro. There I swam in kinds of fjord with clear water and gorgeous natural surroundings. I swam between the cruise ships and constantly felt those very cold bubbles of water. It really was a wonderful experience. We are part of nature ourselves but we don't think about that and we don't live that way. That must change. We should become more aware.'