Buoyancy
Fig. 31: Buoyancy excercise: At the left entrance someone has placed a square made of platic pipes where one can swim through. Unfortunately the water was quite hazy there. — Nikon D200, Nikkor 10.5mm DX Fisheye, Riedsort, Lake Lucerne, 16 August 2009 Nikon D200; Δt=1/180 s; f=10.5 mm; f/7.1; ISO 400; 16 August 2009 14:13:03