After a while you just stop doubting the power of Google. Now for your planetary voyeuristic pleasure the big G has released version 5 of the eponymous Google Earth, bringing with it the power to turn back time and plumb the ocean depths. Or something like that.
Anyway, the new beta adds some cool imagery of the ocean floor along with 3D shipwrecks and educational maritime videos. Also newly included is the fourth axis, allowing you access to historical imagery for certain locales so you can turn back the clock and see how things have changed over the years. The final big new feature is the capacity to make "free-form tours" with soundtracks and narrations.
As before, Google Earth is a free download with the more feature-laden pro version available for $400.