We wrote this book to help you understand what is happening and why it happens before, during, and after a dive. Many of you will be preparing for an exam to become a dive professional. This is book tells you all you need to know, no more, no less. We will start off easy with a short introduction to the dive environment, where we look at tides, currents, waves, coasts, ecosystems. Why are there usually two tides per day, but only one Moon? Why do currents follow a certain pattern over the globe? What makes waves big, how do they break at the beach? How many different types of coasts are...