The third waterfall stop was actually two different falls: Lower Proxy Falls and Upper Proxy Falls. A short circuit hike will take you past each.
The third picture is of the pool that the Upper Proxy Falls drains into. Notice anything weird? The picture may not make it easy to tell, but the water flowing in on the right side never flows out of the pool. It must "drain" straight down into the volcanic rock. My first theory was that someone had installed a submerged pump that pushed the water back to the top, to tumble back down again. But I found no evidence of a pump or pipes, so I came up with that other, less interesting, theory.