Depends on your definition on "regular", doesn't it? Joe Average on a fish-watching trip in the Bahamas? No, you can go to about 30 meters using regular air or

Depends on your definition on "regular", doesn't it? Joe Average on a fish-watching trip in the Bahamas? No, you can go to about 30 meters using regular air or nitrogen-oxygen mixtures. Some technical diving enthusiast planning a 50-stage 20-hour dive to 175 meters, just because the hole is there? Well, you absolutely need some other gas in there, and helium is currently the popular choice.