TDI and PADI Tec are the most widespread. IANTD Thinking Diver since 1985. GUE unified configuration and team focus. Prerequisites: fine buoyancy, no-fin propulsion, bubble control, lost-visibility drills.
Divers wanting to enter the technical diving world debate between agencies (PADI, TDI, GUE/DIR, UTD, IANTD) and look for trusted instructors in their geographical area. The DIR vs. Hogarthian debate reflects philosophical differences about equipment and procedures. Discussions cover which certifying agency provides better real-world preparation versus which simply certifies more quickly.
TDI and PADI Tec are the most commercially widespread, with progression from Tec 40 to Tec 65 and Trimix Diver. IANTD, founded in 1985, bases its model on the "Thinking Diver" concept with emphasis on physiological understanding and autonomous planning. GUE applies a more rigid system with unified equipment configuration and a strong team-oriented approach. Technical training requires prior mastery of skills such as fine buoyancy, no-fin propulsion, breath control, and lost-visibility drills.