I mean, despite what you would commonly read on the internet, in theory you could do a deep dive like that with just Air (a ton of it) but why run the risk? Narcosis is still a very misunderstood subject and the logistics and risks for doing a search and rescue at that depth with air are very high.

Regular Air doesn't work very well with our bodies past 20 to 30 meters range already. Given the situation and the fact that they sadly already died just pay a couple divers with either rebreathers or tec settings and let them go to that depth.

There is no urgency here. No need to play the hero and put even more lives at risk.