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Except in a cave/wreck, you can always go directly to the surface. The question is whether you will develop symptoms. And if so, how severe? The difficulty in defining a boundary is that it's really a continuum, though the size of a common single tank has long been a strongly limiting parameter.
Overhead is overhead, hard or soft.
I agree. But soft overhead is a continuum. You could surface and develop DCS. But under other circumstances you could surface and just have some mild skin bends. Or you could surface and just feel strangely fatigued. Or you could surface and have no signs or symptoms or fatigue whatsoever. You can always go directly to the surface through a soft overhead; the question is how much risk does it involve.
Cool, but the question was when is it a tech dive vs rec dive, not how much risk is involved.
Your assertion was that if you can go directly to the surface it is a rec dive, and if you can't go directly to the surface it is a tech dive. That is not true because--at least in open water--whether you can go directly to the surface is not the determining factor; rather, it's whether you can go directly to the surface with little to no risk. You can always go directly to the surface in open water, regardless of whether it's a tech dive or a rec dive, but the consequences may differ.
Yes, with mixed gas, I mean a gas switch. And Trimix of course. But usually with Trimix you have at least 1 gas switch
No, it is not. SSI's Decompression Diver is a specialty course within their Advance Scuba Diver program. Their technical program starts with Extended Range Foundations.
