As the provocative title suggests, it literally means bathing in your birthday suit.
No joke here, it’s all real and in the hot baths it is really required to be naked save for a small towel. Now, I would imagine that the Nordics would be familiar with this – since there are also geyser baths in places like Iceland. So while ‘skinny dipping’ would seem to be negative in the western sense, it is perfectly normal here. Japan being on the pacific ring of fire means that hot springs (they are called ‘Onsen” here) are numerous.
But etiquettes still apply, and it is extremely important that one clean oneself before dipping into the hot soothing mineral water. This will help assure all other users that the water remains hygienic. Also, most Onsen is designated single-sex only and mixed baths are less occurring. That should help the shy ones.
Only when you have dipped into the piping hot broth of mineral water (each spring has its own unique mix), will you know the feeling of warmth especially during this period of harsh cold winter.
As the temperature of the water varies, you will to be careful how long you stay in the bath. The recommendation is that if temperature is >42°C, stay no more than 10 minutes submerged in the water. Even for baths with a lower temperature if is not recommended to stay more than 20 minutes. It is actually my own practice to dip for 5 minutes and then sit out of the water for 1-2 minutes before submerging into the alluring warmth of the spring.
In most hot-spring inns (Ryokan they call them here) or public bath houses, there are dressing areas where you can not only dry your self and re-clothe, but also preen yourself. All manner of personal care amenities are usually available.
During our drive through the five lakes of Mount Fuji, we had the pleasure of staying in two Ryokans and experiencing the mineral riches of two different springs.
Normally it is not allowed to take photos in the bath, but we had arrived at 3pm and went to the bath when there was nobody. So, the trick is to either bath when nobody else wants to, or bath very late when no one will do.
Really enjoyable way to end your day especially these last few days of sub-zero temperatures!