The Revised 7th Edition Change A of the United States Navy Diving Manual incorporates many major changes from the previous versions and has been extensively modified.  This manual incorporates Change A corrections from April 2018 and is the most up to date version available. To this extent redundant information was reduced and readability was increased by consolidating information to one location.  All procedures and operations have been updated including updated decompression tables to correct profiles known to have caused issues with above average risk of DCI. The material has been clarified and long unwieldy paragraphs have been broken into bullets where possible.  Information has been moved to the most relevant chapters for example all SCUBA information is now in the SCUBA chapter etc. For many decades the US Navy Diving Manual has been the ultimate reference source for the diver.  Potential readers may feel challenged by the sheer size of the work. At just under 1000 A4 pages this manual is unsurpassed in technical detail and depth. As the ultimate diving reference work the book contains everything you ever wanted to know about diving and many aspects that you could never imagine! The manual is however surprisingly easy to read and is composed of five individual chapters. The chapters are as follows: chapter 1: Diving Principles and Policies; chapter 2: Air Diving Operations; chapter 3: Mixed Gas Surface Supplied Diving Operations; chapter 4: Closed Circuit and Semiclosed Circuit Diving Operations; chapter 5: Diving Medicine and Recompression Chamber Operations Each section has been extensively researched and is widely regarded as the technical standard for diving information and procedures. The manual is easily referenced and used internationally by recreational, commercial, and military divers because of its authoritative and approved procedures. This Revision 7A contains the most up to date decompression tables, and techniques for avoiding decompression sickness.