Noticed in the Xbox 360 version of the game, the water near the Mirelurk Eggs of the Georgetown West exit sometimes glows a highly fluorescent toxic green color. This has also happened in other locations.
Confirmed with more details. It was normal at first pass (entered via Arlington Utility), but upon exiting to Georgetown and immediately returning the almost white glow was throughout the area. So it may be re-entering from bright daylight that causes the glitch. (Due to loading, at least on the 360, light settings may lag behind the scene by half a second. Especially funny is to fast travel from e.g. Megaton to an outdoor location and the day/night turns immediately to night/day respectively.)