Google updated it's Google Earth app for iPhone and iPad this morning, including Retina Display support and oceanic layer content that was previously unavailable to iOS users. With this new update, you can now zoom in below the surface of the ocean and view the deep trenches and geography of the ocean floor.
Taking a look at the underwater bathymetry on iPhone 4 Retina Display is, simply put, amazing, and a new experience for users on the go. You'll have to see it for yourself to truly understand what I'm trying to relay in this post.
Google Earth is a free app on Apple's App Store, and can be used with any iDevice.