This is another one of those "When did they put that there?" realizations. This is a relief carving on City Hall that I recently noticed. It's incredibly detailed with a lighthouse in the background and a hermit crab just to the right of the swimmer.
Apparently this is one of four relief carvings by the entrance to City Hall that "represent ... four principle concerns of city government: playgrounds, schools, parks, and water supply". This is probably the water supply panel. Now, I want to go back and look for the other three.