This lake is popularly otherwise known as Wildcat Lake (Jezioro Żbik), or Gutkowskie Lake and Żbikowe Lake. It is located in the north-western part of Olsztyn, between lakes Ukiel and Redykajny. The area covered by this reservoir is approximately 18.5ha and its depth reaches 30.4m. It is surrounded mostly by woods, wetlands and wastelands. Part of the shoreline, counting a total of 1,620m, was overbuilt; for instance a large hotel facility was erected on the northern side. The edges of the lake with their wild unguarded beaches are a popular recreational area. With clear water (classified as second-class purity), Tyrsko Lake is a great place for divers. It is also recommended for anglers, primarily those who catch predatory fish such as pike and perch. In 1957, the lake gained the status of a nature reserve due to the presence of lake quillwort (poryblin jeziorny) which is very rare in the Masurian Lake District. Due to the disappearance of the plant, as a result of the use of the lake, however, the nature reserve was liquidated in 1987, but still remains very attractive.