Fig. 24: That's an old ice diving hole. It's no longer safe to use because the ice has molten due to the warm exhaled breathing air of the divers. DiveZone ice diving event, Lake Klöntal. Nikon D3; Δt=1/500 s; f=28 mm; f/11.0; ISO 200; 1 March 2014 12:08:18
