Diving Speigel Grove without Nitrox...

[MauiScubaSteve]

"half stops" are of questionable significance for the vast majority of recreational divers, afaih.

 

[Mr Carcharodon]

Maybe I'm behind the times but I don't remember these multiple stops from any of my classes. As a recreational diver I've always followed the rules:
1. Do not exceed NDL time.
2. Minimum of 3 minute safety stop at 15'

I frequently stay at 15' for a few extra minutes, in the slight chance that I could see a passing pelagic.

Has this rule changed or are you all providing tech planning to a rec diver?

Well there are two prevalent model about how to decompress and the result in different ascents. Bubble models call for deep stops. There is good reason to think these work since relative levels of bubble formation have been demonstrated in the lab. But the situation in human beings is more complex. Also outcomes depend on the procedures followed. Over staying deep stops can make things worse just because the gas load has gone up. Finally it's hard to know if one method is better than the other. The risk for both approaches is low. So if you take the difference between two values close to zero you'll likely find the difference to be within the noise.