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SDI vs. TDI vs. ERDI – What’s the difference in the diving courses?
by: Jon Kieren
SDI vs. TDI vs. ERDI, three agencies under one company…But why? And what’s the difference between them?
We get questioned a lot on what the difference is between SDI, TDI and ERDI courses, so we decided to put it out there where it’s easy for everyone to find when they start doing research.
When prospective students start looking into taking SDI, TDI, or ERDI courses, they will often quickly realize there’s actually a lot of overlap. We have SDI and TDI Nitrox, SDI and TDI Sidemount, SDI and ERDI Dry suit, SDI and ERDI Full Face Mask, and many more. But why?
It’s easiest to explain the overlap by first explaining the purpose of each agency:
SDI (Scuba Diving International) courses are designed primarily for sport divers. These divers are recreational divers whose intentions are to remain (relatively) shallow, within no decompression limits, in open water (non-overhead) environments. These divers are either just beginning their journey, or are looking to advance their diving skills to enhance their diving experience within these limits. SDI courses are the foundation for TDI and ERDI programs when a diver is looking to extend their limits or work as a public safety diver.
TDI (Technical Diving International) courses are designed for the recreational diver looking to extend their limits and journey into decompression diving, overhead environments, and using rebreathers and mixed gasses. TDI courses range from entry level nitrox through advanced mixed gas CCR and full cave diver. These courses take an in-depth look at the physics, physiology, technology, and advanced skills required to survive in a very unforgiving environment where divers do not have direct access to the surface.
ERDI (Emergency Response Diving International) courses are developed for training divers to conduct working dives in the public safety realm; mainly police, fire, and federal agencies. These courses train divers for rescue and recovery operations in hazardous environments, and need to meet certain local and federal regulations for workplace safety, as these divers are diving for their occupation.
So why would a diver choose an SDI Nitrox course over a TDI Nitrox course? Or an SDI Dry Suit course and not an ERDI Dry Suit course? The simplest explanation would be “it depends on what they intend to do with the certification”. We’ll break some of the key differences down between some of our most popular courses here:
SDI Computer Nitrox vs. TDI Basic Nitrox Diver – SDI Computer Nitrox is a very basic introduction to diving nitrox utilizing a personal dive computer, within no-decompression limits. Dive planning, calculations, and knowledge development is kept to the essential key topics that a diver will need to dive nitrox effectively. TDI Basic Nitrox goes a few steps further and introduces more involved dive planning, calculations, and basic decompression theory for the diver who is planning on furthering their education and moving into decompression or rebreather diving.
SDI Sidemount vs. TDI Sidemount – SDI Sidemount Diver covers basic topics and skills to prepare a diver to dive utilizing sidemount as an alternative equipment configuration to the traditional backmount, while staying within no-decompression limits. TDI Sidemount Diver is intended for divers who are already trained technical divers, or are planning on moving into technical diving, wishing to conduct decompression or overhead environment dives utilizing sidemount as an equipment configuration. The basic knowledge development and skill sets are similar; however the TDI course will go into more depth on subjects such as: gas planning using independent cylinders, carrying additional stage/decompression cylinders, trim and buoyancy control, etc.
SDI Dry Suit vs. ERDI Dry Suit- SDI Dry Suit Diver covers the knowledge development and skills necessary to conduct recreational dives using a dry suit. The ERDI Dry Suit course covers many of the same topics, but will address additional concerns for public safety divers including environmental issues and decontamination procedures.
So while the courses may seem similar at first glance, you can probably see already that the topics covered within the courses are going to depend on what the student is planning on doing with that certification. For more detailed descriptions of these and other SDI, TDI, and ERDI courses, please see our course description pages here: