The title hints that this is the reason for the country's high score in happiness surveys such is this one: http://www.independent.co.uk/news/world/europe/denmark-happi... . While I don't think it's that simple I can forgive the author, the title "A survey on Icelandic swimming pool culture" just doesn't have the same ring to it. Usually when I see these surveys the first question that pops up is "How do they measure that?" and it seems journalists generally are not to keen on pursuing that question.
My point is that isolating one thing from a culture and pinning that down as a "cause for happiness" seems a bit silly to me. But apart from that the article is pretty accurate.