Pennock photographs a diver, most likely inspecting the gates at the Newboro Lock. While he dives, his assistants at the left power the compressor that keeps him breathing. On the right are onlookers who watch him intently, like a group of fans captivated by an important celebrity.

Some decades before the invention of the on-demand breathing apparatus, this would indeed be a fascinating occurrence to observe.  Once again Pennock captures for posterity the awe of the occasion.