Slevenian largest alpine lake is Krnsko jezero (Krn lake). It is 390 m long, 150 m wide and the deepest point reaches 17,5 m deep. The water level fluctuates by about 2 m, the highest level is at the beginning of the summer.
Don’t forget – high alpine lakes are isolated and very sensitive ecosystems. Please appreciate and admire their beauty without swimming in them, (which is also not allowed).
Info about trails:
Huts in Julian Alps: https://en.pzs.si/koce.php?reg=3
Photo: Google maps