The brown trout (Salmo trutta) is restocking in this lake (Oostvoornse meer).
Fly fishing is used to catch the trout. The artificial fly is cast using a fly rod, reel, and specialized weighted line.
It is a very nice sight how the end of the line warps over the water. However I think this fisherman was more interested in just floating there because his line didn't sway back and for much.