The ERDI Emergency Response Diver Student Manual is the text-book literary assistant to the ERDI certification course. The emergency response diving environment is unique in many ways from any other diving environment or diving activity. Recreational divers are trained in such a manner so as to ensure maximum enjoyment from diving activities that involved minimal risk. Emergency response diving also differs from technical diving. Technical divers may push depth limitations and bottom times, they may dive in caves or in shipwrecks, but they are still for pleasure and in situations in which they are very controlled and calculated amounts of risk. The Emergency Response Diving program is more difficult than the previously mentioned courses, and it is this difficulty that is designed to help you meet the challenges of the job.