What are some of the unique dangers in a 1200' dive, as compared to a 800' dive?

[Akimbo]

In one of the other threads, someone mentioned that a 1200' dive is a totally different game than an 800' dive...

That is sort of vague or I’m not in the right mindset to appreciate it. I see 1200' as having the same well-understood constraints as 800'. As with any dive, the logistics increases the deeper you go and the longer you stay.

This whole Scuba depth record mentality comes down to who can minimize logistical support the most and still survive. It’s not about who can go the deepest and accomplish anything remotely useful.

 

[Michael Guerrero]

I think the two biggest were already mentioned, particularly for the kind of dive Dr. Garman tried. HPNS only gets worse the deeper you go, likewise with CO2 retention due to gas density.

For HPNS, Nitrogen and Helium work in opposite directions on your nervous system, if I remember correctly. And you have to save room for O2. There is a physical limit for all these for your body to function. Helium offsets the narcotic effects of Nitrogen, but Nitrogen offsets the nervous system effects of rapid compression, where the use of Helium is often large. O2 becomes increasingly toxic the deeper you go.

For CO2, at some point the work of breathing, based on gas density, becomes too great for muscular respiration...even without any additional exertion. I don't know the limit of this either, but the deeper you go the worse it is.

So, basically, nature conspires against you the deeper you go. Everything hard at 800 feet is harder at 1200 feet, and the margins for error (whether human or physiological) are that much thinner.