On Thursday, I went down to the river and found a group of college-age kayakers, whom I'd guess belong to a kayak "circle" at their university. These sorts of clubs/circles are one of the most important parts of university life in Japan since it's said to be more about learning relationships and positions in society than actually studying academic subjects. I've friends who consider their university years as a four-year vacation. Folks need some time off after years of memorizing for the entrance exams for college.
*Japanese seem to tolerate and accept a lot more direct human involvement in nature and alteration of nature for improved aesthetics than Americans (US & Canada) and perhaps other westerners do. This is not only my observation, but something I have read or deduced from several sources.