Not to mention tank pressures are a tangible limit. A full 3000psi cylinder would be "empty", or equalize with ambient pressure, at a little deeper than 6700ft.
Yes, that is far deeper than the 2000ft gas density limit, but it's still a reduction in available gas, and certainly a hard floor which could never be passed no matter what special gasses would be used. Even at 2000ft, you can cut nearly 1000psi from your available gas supply.
Narcosis, HPNS, O2tox, all present very real physical and logistical challenges.
For a wet dive to 2000ft, an O2 level of 1.6% would result in a PO2 of about 1.0. That would be an extremely tricky tank to mix, given that O2 analyzers are barely accurate to more than 1%, and are pretty inaccurate when you get much below 10%.
Going deeper further compounds the problem, but even a dive to 1000ft on scuba faces similar challenges.
Realistically, few of us will ever see the far side of 350ft and make it back to talk about. Deeper than that and you get into the realm of "why".
Brass bawls have no place in diving, and 300-400ft is the max depth where you can spend enough time to actually accomplish anything without incurring unrealistic decompression obligations.
Doing it to break a record is a reason, but, IMHO, it's a very stupid reason to do a high risk dive with absolutely zero benefit beyond an ego stroke.
Yes, I view freediving record attempts with the same distain, and Audrey's death was a tragic waste of human life.
Keep in mind that the divers in the link you posted were supposed to have done that dive this month.
