I have found getting certified in a skill like diving or ropework is not the point. It's what skills do you bring to the thing you dove or climbed to fix? Do you know hydraulics, basic electrical work, troubleshooting, etc. Learn those first. An old dive buddy of mine used to say you can teach a monkey to dive, but what can he do when he gets there? I need skilled people.
Also there are many types of technical diving: commercial diving and deep sea diving, wreck and cave diving, underwater welding, salvage, show divers (fairly new - since the show 'O' in Las Vegas - divers that escort performers underwater for water shows), and many more.