Dumb question, but... how deep can you go?

[Tassi Devil Diver]

One of the most famous divers of the twilight zone is ichthyologist Richard Pyle.

Thanks for posting that link, I saw it years ago but could not find it again.

 

[Alex Ouroboros]

Somewhere around 500’ seems to be practical stopping point. There are instances of going deeper, but the risks and complications really skyrocket much past 4-500’.

Gas density is huge. HPNS becomes a factor. Not to mention the deco obligations one incurs really gets out of hand. There’s thermal, hydration, and nutrition issues to contend with on long dives.

In extreme cases, people are using experimental gases like hydrogen to help with some of those above factors, but this obviously has its own set of considerations.

Pretty much exactly what I would agree with,
To expand slightly, the problem becomes your redundancy or back up, at 100m (300’) even a short visit of 10mins requires 3 x Ali80,s in case of failure with appropriate gasses, to stay longer or go deeper starts to require either a truckload of gas, (I don’t like going in with more than 4 ali80,s personally) or a bailout rebreather, open circuit requires so much gas that these depths are rarely dived in this way now.

 

[stiebs]

So what is the maximum reasomabke depth for recreational CCR use?

Have a look at this video:

 

[arkstorm]

The limiting factor of how deep you can take a CCR is the human body, not the machinery.

You can always build the machinery to withstand greater pressures if necessary. You can always engineer redundant bailout systems, etc.

However, the two competing human factors in the equation are HPNS and work of breathing.

Susceptibility to HPNS is a matter of individual physiology -- it just is what it is.

To reduce work of breathing requires use of lighter diluent gasses and very recently certain groups, as discussed in the video above, have experimented with hydrogen -- but this is at the very cutting edge, it is not what anyone should consider to be a practical solution for recreational technical diving at this time.

 

[RedSix]

certain groups

It is a single group. And it was a single dive up to now.
n = 1

 

[admikar]

Have a look at this video:

I wouldn't call that reasonable.