A diving instructor is a person who trains and usually also assesses competence of underwater divers. This includes freedivers, recreational divers including the subcategory technical divers, and professional divers which includes military, commercial, public safety and scientific divers. Depending on the jurisdiction, there will generally be specific published codes of practice and guidelines for training, competence and registration of diving instructors, as they have a duty of care to their clients, and operate in an environment with intrinsic hazards which may be unfamiliar to the lay person. Wikipedia