We just stood there for a few minutes, our shoulders brushing, as we watched the water ripple under the glow of the moon.
Water, moon, abandoned building on the docks- it mirrors the earlier scene on the dock, but with a key difference - these docks are not floating out in the middle of the lake, they are secure and so closer to civilization. Docks are a place of transience - people come and go and bring things from other parts of the world, and they either sail off or go back to civilization - it's like a border between the unknown and security. So having this be the location for their post-prison conversation shows that they need to wash away their untruths and talk about the past, while also acknowledging things will change as they head back to civilization - because things have changed in the real world as now and they need to be made sense of near the water.
Plus, the abandoned building is symbolic of Devon's dreams for the future and Maddox's commitment to Devon, that stands firmly between the water, where truth is revealed and they are renewed - and the path back to civilization, where they work and life is difficult. Whatever is going to happen here, it's going to be huge - even bigger than the time on the dock in the lake where they admitted they had feelings for one another and were open with each other for the first time - because at that point, Devon was still unwilling to change. With what's happened now, in prison, Devon has made some realizations about himself.
