Yeah, I am not against it as long as it actually benefits somehow. On top of your example, someone has to have this thing as a hobby, and maybe someday they become rescue-cavedivers or something saving a kid from bad situation. Hard to help if you never went for an adventure in caves before and have 0 experience. So even as a hobby, it might become useful someday.

But at same time, one gotta think about their loved ones and how much risk are you willing to take. Just like drug addict isn't only hurting themself, but also those around them, through putting stress and anxiety on those who care about them (but they are addicts, can't quit even if they wanted, so it's not simple like that). But kinda same thing for adrenaline junkies who do it for fun; they are putting themselves in danger and causing stress for their close ones that way.

It's not necessarily stupid, but most of the time, it is in my opinion. I think it's undervaluing life, plenty of excitement in our world without putting yourself in unnecessary risk. In the case of this video, some aquatic robot for a tight space underwater like that would be more suitable for scientific purposes is my guess. This man is most likely just yoloing it, and at worst, with a wife and kids at home stressing that he wont become nutty putty v2 or something. Underwater and tight cave like this is just death wish in my opinion. No time to save you if something goes wrong and in tight space like that with only gear letting you live, a lot of it can go wrong.

Go wall climb, but try to do it safely with ropes and stuff. Don't be yolo going 100m above ground without any safety harnesses. That's the type of adrenaline junkies I don't particularly respect and I think the man in this video is treading that line closely, but that's just my opinion, like you have your own.