I spent a late autumn many years ago working with aquatic vegetation of heavily acidified lakes of Southern Norway. Some of these had extremely clear water due to the low pH, sometimes dropping even below pH 4 to reach the acidity level of raw citric acid (or Coke). Submerged bog mosses in particular
Sphagnum cuspidatum and i
ndunatum, were seen frequently. Some times a few specimens of Bladderwort
Utricularia or Least Water-Lily
Nuphar pumila made a change to the moss beds.
In order to take the capture below, showing fallen autumn foliage of Downy Birch
Betula pubescens floating on th surface of one of these acid sites, the camera exposed the film for about 2 minutes on its 'A' setting. The water surface was dead calm and I had to behave like a drowned statue during the exposure lest the shot would be ruined. Not easy at subzero temperatures end of September in a subalpine area
I think the UW-Nikkor 15mm f/2.8N showed off its qualities in this photo.