Endurance Diving

[D-Boy]

What are the effects on the body from endurance diving (Two hours +)? I've heard stories of dives reaching as far as nine hours. I'm sure it's possible but do you need specialized mixed gas rigs? If so, what? I know SDV Teams do this on a regular basis so I would kind of like to know how. Are there Increased off gasing plateus, etc. Any information is great!!!!
D-Boy out.