Formed in 1994. TDI is similar in content and make-up to IANTD but is considered to be the largest specialised training agency with over 10,000 instructors ready to teach the ways of technical diving.

In 1999 a sister company, Scuba Diving International was launched. This branch of TDI caters to the recreational diving as opposed to the technical aspects of TDI.

The TDI Diver Hierarchy

Tech Diver

Introduction to Tech Diving

Nitrox Diver

Advanced Nitrox Diver

Deco Procedures Diver

Extended Range Diver

Trimix Diver

Advanced Trimix Diver

Tech Instructor

Nitrox Instructor

Advanced Nitrox Instructor

Deco Procedures Instructor

Extended Range Instructor

Trimix Instructor

Advanced Trimix Instructor

ANDI	BSAC	CMAS

DAN	DSAT

IANTD	NAUI Recreational	NAUI Technical

NOAA	PADI	TDI