Book excerpt: Diving is an exciting sport as well as a requirement of some vocations such as commercial diving, military diving, public safety diving, and scientific diving. In sport diving, most learn to dive with a half mask to cover their eyes and nose. A second stage regulator supplies their breathing gas (air). This method of diving is safe, simple, and time-tested over the last half century. The diving scenarios that appear throughout this guide are actual situations that occurred to divers. The author spoke with these divers and recorded their experiences for the educational benefit of the reader. The scenarios are described as the author interpreted each of the experiences. All the divers and the people that might be associated with their dive experience should not be faulted for any bad situations they came to be in. Every person has had some type of mishap in life, and the purpose for sharing these scenarios is to teach and help avoid future incidents that might cost someone their life.