Our mask is designed for surface snorkeling. You may be able to dive down a few feet, but serious free diving is not recommended.
An important aspect to free diving is the ability to equalize the pressure in your ears as you descend. Most people equalize by pinching their nose while blowing out air. A full mask doesn't allow for this. There are other ways, but usually it requires a more advanced user. For great information about free diving, you can visit Deeperblue.com. This article provides most of the information you need to learn about free diving.