About a month before I started studying the PADI Open Water manual (that you receive by post if you choose the fasttrack course), I bought a few books to get myself familiar with the concepts behind scuba diving.
First I chose "The Divers Handbook" from Alan Mountain, because it includes 50 pages dealing with coral, fish, and dangerous underwater creatures. Then I felt the need for something more technical and went for Dennis Graver's "Scuba Diving".
The book has a lot of background information illustrated with simple diagrams: the "Diving Science" section goes into the details of Guy-Lussac's law, Henry's law, partial pressures, and air consumption formulas.The "Dive Planning" section, while it uses USN tables (United States Navy) and not the RDP tables of the PADI course, includes dive planning problems and solutions and explains how to compute a letter group after repetitive dives.
You also find some interesting information about the physics behind waves, surf and currents in the "Diving Environment" section.
A very usefull book that allows you to go a little deeper into scuba diving theory than the PADI course does.
