Google Earth 3.1 for iOS let you explore underwater landscapes and terrain on your iPhone, iPad, and iPod touch. "Once underwater, simply swipe the screen with two fingers to 'look around.' You can always reset your view by clicking on the north arrow on the iPad, or on the compass on iPhone and iPod," explains Google.
Also, added the "Ocean" layer, which features hundreds of photos and videos from more than 100 contributors curated by the Sylvia Earle Alliance. This version also includes native support for new Retina display, which means that if you've an iPhone 4 or new iPod touch, you'll get to enjoy an even sharper view of the world.