The included case protects the Garmin Virb not only from water, but also from impacts.
At first, I thought that the small opening for the speaker would cause some problems, if the camera was put in water. So I submerged it, and it came out working fine. Garmin says that it is waterproof for up to 40 m, but it was difficult to test this so I kept it submerged for two hours. After pulling it out, it worked just like before.