High Quality Content by WIKIPEDIA articles! Technical Diving International (TDI) is the largest technical diving certification agency in the world. As one of the first agencies to provide training in mixed gas diving and rebreathers, TDI is seen as an innovator of new diving techniques and programs which previously were not available to the general public. Training with TDI has provided divers with the opportunity to see such wrecks as the Andrea Doria, Luisitania and the Prince of Wales. TDI divers have explored underwater caves in Spain, Australia and Mexico and assisted as support divers on world record freedives done in the Red Sea.