You are Catherine Dubont. The Laser Drill opened a cavern 10 miles beyond the surface of the earth. They installed an elevator which you and some others took to go down all the way into the world of the unknown. As you almost reached the bottom of the drill hole, the elevator rope broke and the cabin dropped down the last 100 feet. Everyone is dead. All lights are gone. The only thing you have left is your modern sonar scanner.
The second demo of SONAR, containing 2 Levels and nearly every single gameplay element.
To install the demo, just double click on the exe. The archive will extract itself and start the installation routine afterwards automatically. This may take some time, because it will look for .NET 3.5 SP1 and XNA 3.0 and install it if not found on your system.
After everything is installed, the game starts automatically.