The Environments

Here are some activities that you may encounter when you decide to start a career as a pro: 

Underwater installation, repair and maintenance
Fabrication of special equipment
Flotation devices maintenance
Gravity surveying
Grouting
Guideline replacement
Hyperbaric chamber operations 
Injection equipment installation
Life support systems construction, operation, repair and maintenance
Marine environmental control check
Medical and emergency care for diving illnesses and accidents
Operation of one atmosphere suits
Operation of remotely controlled vehicles 
Operation of diving bells 
Platform construction, inspection, maintenance and removal
Rock drilling and blasting
Salvage
Search and recovery
Seismic surveying
Sewage line installation and maintenance
Site surveys prior to installation
Submersible operations
Surface geological appraisal
Trenching o Underwater jetting
Underwater painting
Underwater photography and videograpy
Underwater surveys
Underwater welding and cutting
Water line installation, inspection, repair and maintenance
Wellhead repair and maintenance

(Can you think of some more ??)

What you need to get in

Here are some general basics to be allowed to enter a course. Remember that this list features basics. Various schools may demand various additions.

Age
Generally, a student must be 18 years of age or older on or before their graduation date. 

Educational Requirements
Applicants must furnish evidence of a high school diploma or a General Educational Development (GED) Certificate, or state-approved high school equivalency. 

Diving Medical Examination
Applicants must pass an approved medical examination administered by a
licensed and qualified physician. Written verification of current tetanus immunization is required. 

Acceptance
All prospective applicants must meet diving center admission requirements. A Admissions Committee will review your application for final approval.

Courtesy of College of Oceaneering