The Fraunhofer Institute for Applied Information Technology FIT just presented an Augmented Reality system for use under water. A diver's mask with a special display lets the diver see his or her real submarine surroundings overlaid with computer-generated virtual scenes.

In the pilot application, an AR game, the player sees a coral reef with shoals, mussels and weeds, instead of a plain indoor pool. Applications for professional divers are being investigated.

Augmented Reality research has made enormous progress in the last few years, creating many exciting, albeit land-based applications. Now, FIT researchers are the first to demonstrate an AR application designed for underwater use. Submerged use is a major challenge for technical systems. They must be waterproof and robust enough to withstand the high additional pressure of increasing diving depth.

FIT researchers built a prototype AR system that meets these requirements. Its main component is a waterproof display in front of a diver's mask. The display lets the diver see his or her real underwater environment plus additional virtual objects. Thus, a run-of-the-mill indoor pool may be visually upgraded to a (virtual) coral reef with shoals, mussels and weeds. An ultra-mobile PC (UMPC), which the diver takes with him in a backpack, detects underwater markers in the video stream from a camera on the top of the diver's mask. Based on the pictures from the camera and on the data from inertial and magnetic field tracking of the diver's orientation, the system generates visually correct representations of the virtual 3D scenes.

As a demonstrator Fraunhofer FIT created the world's first mobile underwater AR game. It puts the diver in the role of an underwater archaeologist searching for a treasure chest. The playground consists of six virtual 'islands' on the sea bed, each with its specific rich marine wildlife. In one of the underwater locations the treasure chest can be found, but it then takes a code number to open the lock. The elements of this number can be found in 'magical' mussels that hide in the other five locations.

The user interface of this novel underwater game is highly intuitive and optimized for the swimming and diving player: It works without any manual interaction devices.

"For the player, our game combines the fascinating sensation of weightlessness under water with the fascination of advanced AR technology, creating a unique exciting experience that may become a new special attraction for water parks," explains Ms. Lisa Blum, one of the researchers involved in Fraunhofer FIT's research on Collaborative Virtual and Augmented Environments. At the same time, the prototype is a robust platform for development work well beyond entertainment applications. Next Fraunhofer FIT studies potential uses of the submarine AR technology to support professional divers, e. g. in the maintenance of bridges, offshore oil rigs or dams.