Google Street View goes under the sea:

[Y]ou can use Google Maps to find a sea turtle swimming among a school of fish, follow a manta ray and experience the reef at sunset—just as I did on my first dive in the Great Barrier Reef last year. … At Apo Island, a volcanic island and marine reserve in the Philippines, you can see an ancient boulder coral, which may be several hundred years old. And in the middle of the Pacific, in Hawaii, you can join snorkelers in Oahu’s Hanauma Bay and drift over the vast coral reef at Maui's Molokini crater.

John Metcalfe explores how they did it:

For this project, Google teamed up with the Catlin Seaview Survey, an international team of researchers based at the University of Queensland devoted to saving the world's imperiled reefs. As the Seaview folks point out, the world has lost up to half of its reefs in just the past 30 years, partly due to ocean acidification caused by anthropogenic climate change. The team's divers are lugging a 360-degree panoramic camera (the "SVII") through the ocean to create a baseline survey of the current health of reefs, which would be a valuable tool for marine biologists. As it stands today, humans have explored a mere 5 percent of the ocean.

Matt Burns splashes cold water on the rollout:

Right now the imagery is very limited. Outside of the links above, it’s rather difficult to find an area to go swimming. Seaview spots are marked with an orange circle that’s only revealed when the Street View icon is dragged onto the map. Even then, these spots only show up when the map is zoomed in nearly all the way. It seems Google announced this service a bit prematurely.