I've just come across an article on the impact of smoking on diving (a part of required GUE reading materials), and I was surprised that in 2015, such an article still had to be circulated... pretty much nobody I know smokes anymore. At the same time, pretty much everyone I know drinks, and I have never come across much of anything about the harmful effects of alcohol in diving, except for that commonly held belief that because alcohol promotes dehydration, it increases somewhat the risk of DCS. Is there more to it? What do we know today about the harmful effects of alcohol in diving?