Originally designated a reserve under the Third Reich in 1937, and then also acknowledged as a reserve under the PRL in 1947,[2] since 1977 the lake has been designated a UNESCO Biosphere Reserve and a Ramsar site, in view of its importance as a breeding ground for water birds such as grebe, rail, moorhen, grey heron, bearded tit, white-tailed eagle, osprey, rust-coloured kite, cormorant and black tern.

The lake is known since many decades as the habitat of the mute swan (Latin: Cygnus olor) – nesting there every year from a dozen to tens of dozen of pairs, and in time of moult arriving in numbers reaching up to 2,000 birds.

[citation needed] Łuknajno covers an area of 6.8 square kilometres (2.6 sq mi), and has a maximum depth of 3 metres (9.8 ft).

The bottom of the lake is 77% covered with brachiopods (Characeae), potworms (Potamogeton), and spearguns (Myriophyllum).

At the banks, there is a strip of reed rush with a small admixture of narrow-leaved cattail and lake bulrush.