Yeah Ok I was naive...but you gotts understand thsat us Aussies girls pine for the beach a lot...
What amazed me was all of the girls being pushed around in tubes by their boyfriends...honestly only me and all the kids under 10 actually got their hair wet...
The web-site for this onsen is awesome, and I want to go just to check it out. But as Odaiba is on reclaimed land, it begs the question as to the source of the water.. I doubt there is a "natural" hot spring nearby. I don't want to be in a Contaminated Onsen
I want the real thing baby.
A friend of mine used to travel to a river somewhere in Gunma where there was hot water bubbling out. They would all jump in, even in winter, with their togs* on and sit in rubber tubes in the middle of the bush. Can't get more natural than that.
*togs is Australian speak for bathers, swimming attire.