First, we are dive professionals ourselves. We worked in many different countries, for many years, with entry level and professional level students, for different dive organisations. We think we know what we are talking about. Marc Luxen has a PhD in psychology with an interest in dive psychology and has lots of experience in writing educational texts. Sally Powell has a MA in graphic design, and has taught and studied teaching the theory of diving intensively for years. We decided we could write a book that might help you. And of course because we thought it would be fun to write it.