Google partnered with countless scientists and organizations worldwide from NOAA to the Navy to create a realistic map of the ocean floor using bathymetry (underwater topography), and there are many "hot spots" to click on to get more information like video, photos, and research data. While it's not like you can quite swim with the fishes, you can cruise the ocean floor and see the depth or relation to the land. And the collection of video and photos is growing all the time, much like the organic nature of Google Earth itself.
There is even a fish tracker that let's users follow the path of an actual shark off the coast of California, a number of shipwrecks near places like Hawaii, and plenty of photos of quirky creatures like the vampire squid. To check it out just download the latest Google Earth and start clicking. For more, be sure to watch the CBS Evening News with Katie Couric tonight.