You can fish for perch and carp in the lake or for trout in the Riviyre d'Argent (Silver River), or just glide around the lake among the swans.
You will be heavily fined for gliding around the lake. 
mnli hypothesis: You will be heavily fined for gliding around the lake.  premise: You can fish for perch and carp in the lake or for trout in the Riviyre d'Argent (Silver River), or just glide around the lake among the swans.