This is one of many very cool swimming holes in Kyushu. For a google map with English-language reviews, pictures and/or videos of spots inside and near Kumamoto, go to
https://www.google.com/maps/d/u/0/viewer?hl=ja&authuser=0&mid=1o-KebOBHntVC_kIfnwFPUeiJWuY
– Kirk
P.S. I learned about this from a post on the KumAJET Facebook group:
https://www.facebook.com/groups/45261511655/permalink/10153998321356656/
